As a researcher, I'm especially intrigued by fungus-growing ants, a group of 248 species that cultivate fungi as their main source of food. They include 79 species of leafcutter ants, which grow their fungal gardens with freshly cut leaves they carry into their enormous underground nests. I've excavated hundreds of leafcutter ant nests from Texas to Argentina as part of the scientific effort to understand how these ants coevolved with their fungal crops. Much like human farmers, each species of fungus-growing ant is very particular about the type, of crops they cultivate. Most varieties descend from a type of fungus that the ancestors of fungusgrowing ants began growing some 55 million to 65 million years ago. Ant farmers face many of the same challenges human farmers do, including the threat of pests. A parasite called Escovopsis can devastate ant gardens, causing the ants to starve. Likewise in human agriculture, pest outbreaks have contributed to disasters like the Irish Potato Famine, the 1970 corn blight, and the current threat to bananas. Since the 1950s, human agriculture has become industrialized and relies on monoculture, or growing large amounts of the same variety of crop in a single place. Yet monoculture makes crops more vulnerable to pests because it is easier to destroy an entire field of genetically identical plants than a more diverse one. Industrial agriculture has looked to chemical pesticides as a partial solution, turning agricultural pest management into a billion-dollar industry. The trouble with this approach is that pests can evolve new ways to get around pesticides faster than researchers can develop more effective chemicals. It's an arms race-and the pests have the upper hand. Ants also grow their crops in monoculture and at a similar scale-after all, a leafcutter ant nest can be home to 5 million ants, all of which feed on the fungi in their underground gardens. They, too, use a pesticide to control Escovopsis and other pests. Yet, their approach to pesticide use differs from humans' in one important way. Ant pesticides are produced by bacteria they allow to grow in their nests, and in some cases even on their bodies. Keeping bacteria as a living culture allows the microbes to adapt in real time to evolutionary changes in the pests. In the arms race between pests and farmers, farming ants have discovered·that live bacteria can serve as pharmaceutical factories that can keep up with ever-changing pests. Whereas recent developments in agricultural pest management have focused on genetically engineering crop plants to produce their own pesticides, the lesson from 55 million years of ant agriculture is to leverage living microorganisms to make useful products. Researchers are currently experimenting with applying live bacteria to crop plants to determine if they are effective at producing pesticides that can evolve in real time along with pests. Adapted from: https://theconversation.com/ants-with-their-wise-farming-practices-and-efficient-nauigation-techniques-could-lnspire-so/utions-for-somehuman-probl~ms-188939 11. Based on the text, how are living bacteria a better option to control pests? A. Living bacteria feed on pests B. Living bacteria are able to change to keep up with the evolving pests C. Living bacteria are a more natural and durable, and less costly means than chemical pesticides D. Living bacteria will not be killed by chemical pesticides, so its durability fits the persistent pests E. Living bacteria has been a succesful means to get rid of pests used by farmers since decades ago

People who drink two or more sweetened soft drinks a week have much hig her risk of pancreatic cancer, an unusual but .... (42) ... . cancer. People who drink mostly fruit juice ... (43) .... sodas did not have the same risk. Sugar may be to .... (44).... but people who drink sweetened sodas regularly have other poor health habits. The high levels of sugar in soft drinks may be increasing the level of insulin in the body, which we think .... (45) .... to pancreatic cancer cell growth. Insulin which helps the body .... (46) .... sugar is made in the pancreas. 46. A. digest B. metabolize c. stimulate D. produce E. apply

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Since Mario is a presenter, he is used to .... in front of the spectators. A. Speak C. Speaking B. Speaks D. Spoke

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Since 1929, physicists have known that the universe is expanding. Most physicists hold that the entire observable universe was condensed into a tiny area of exceptional density and that this initial mass exploded outward in what is commonly referred to as the "Big Bang." The universe has been expanding steadily ever since this cataclysmic event and most physicists naturally assumed that this expansion must be gradually slowing down. Some theorists even predicted that the gravitational pull of the universe would cause the eventual contraction of the universe-the "Big Crunch." However, in 1998, a team of observers studying supernovae made a shocking discovery. Instead of slowing down, the expansion of the universe is accelerating. In fact, the acceleration appeared to have begun some 10 billion years ago. Later measurements of the cosmic microwave background and a survey of the distribution of galaxies seem to corroborate the initial finding that the expansion of the universe is indeed accelerating. Cosmologists believe the most likely explanation for the acceleration of the universe's expansion is an entity known as dark eriergy According to theory, dark energy should account for approximately twothirds of the total cosmic energy density. It also is believed to be gravitationally repulsive and diffused throughout the areas of space unoccupied y galaxies. Although theoretically possible, dark energy, if it were found to exist, would provide theorists with a number of difficulties and perhaps even require an extensive rethinking of fundamental physics. Some cosmologists believe that the existence of dark energy impl ies the existence of subatomic particles more than thirty orders of magnitude smaller than the electron. Others have tinkered with Einstein's theory of relativity in an attempt to account for the perceived effects of dark energy. Such drastic revisions to long-held tenets have encouraged some physicists to seek a more conventional solution to the accelerating universe enigma, one that does not invoke the specter of dark energy. These theories posit more mundane explanations, such as the aggregate gravitational effect of interstellar dust. Recently, four independent groups have found evidence of the integrated Sachs Wolfe effect, a phenomenon linked to the presence of dark energy. The passage is primarily concerned with .... A. defending an innovative theory B. comparing competing scientific theories C. detailing the ramifications of a finding D. describing a problem and its possible solution E. proposing a new approach to cosmology

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Forget lions, tigers, and bears. When it comes to the art of war, army ants are among the most frightening creatures on earth. With powerful mouth parts, these ighters can skillfully cut creatures much larger than themselves into pieces. Acting together in great number, army ant colonies succeed at making tens of thousands of such kills each day. Their capabilities do have limits, though. Contrary to popular belief, they almost never take down large animals or people. One of the best places to observe army ants is Barro Colorado, an island in a lake creates by Panama Canal. The island is home to as many as 50 colonies of Eciton burchellii, the most studied army ant in world. It is one of 150 types of army ants in the New World; more 170 other types live in Asia, Africa, and Australia. The colonies of this army ant are huge, ranging from 300.000 to 700.000 ants. They never stay in one place long, moving from nest site to nest site. Linking legs together, they use their own bodies to form enormous nests called bivouacs, which they hang beneath a fallen tree. There they stay for about 20 days as the queen lays as many as 300.00 eggs. When the ants go hunting as many as 200.000 of them leave the nest in a group that broadens into a fan as wide as 14 meters. This swarm raid takes a slightly diferent course each day, allowing the hunter to cover fresh ground each time. Protecting the ants wherever they go are soldiers, recognizable by their oversized jaws. If their frightening looks do not scare enemies away, soldier also have a powerful bite and the attack is often suicidal. Because their jaws are shaped like ishhooks, the soldiers cannot pull them out again. Amazonian tribes have used soldier ants to close wounds, breaking of the bodies and leaving the head in place. Eciton burchellii are blind and cannot see what a head of them is, but they move together in such great numbers that they can easily kill the non-army ants, insect and other small creatures that constitute their prey. When the groups happen upon a break in the path, ants immediately link legs together and form living bridges so that the groups can move forwards without any delay. In Japanese the word ant is written by linking two character: one meaning “insect”, the other meaning “loyalty”. Indeed, individual ants are completely loyal to their fellow ants. They display many examples of selless cooperation that, while certainly extreme, cannot fail to win human admiration. In which paragraphs of the text author mention the sight of army ants? A. 2 B. 3 C. 4 D. 5

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The author had died before his book __ . A. has been published B. had been published C. would be published D. was being published E. was published

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