The text is for questions 20 - 23.

    The sense of taste is one of a person’s five senses. We taste with the help of taste-buds in the tongue.

    There are four main kinds of taste: sweet, sour, salty, and bitter. All other tastes are just mixtures of two or more of these main types.

    The surface of the tongue has more than fifteen thousand taste-buds (or cells). These are connected to the brain by special nerves which send the so-called ‘tastes messages.
When the tongue comes into contact with food of any kind, the taste-buds will pick up the taste. The nerves then send a message to the brain. This will make us aware of the taste. All this happens in just a few seconds.

    There are four kinds of taste-buds, each of which is sensitive to only a particular taste. These four groups are located in different parts of the tongue.

    The taste-buds for salty and sweet tastes are found round the tip of the tongue and along its sides. Sour tastes can be picked up only at the sides of the tongue. The taste-buds of the bitter taste are found at the innermost edge of the tongue. There are taste-buds at the centre of the tongue.

    The senses of smell and sight can affect taste. The good smell of food increases its taste. Similarly, attractive colours can make food appear tastier and more delicious. If food does not smell good or is dull-coloured, it will look tasty and may not taste good at all.

    Very hot or cold sensations can make the taste-buds insensitive. Food that is too hot or too cold, when placed in the mouth, will have no tastes at all.

23. The purpose of the text is . . . .