Question 33-36 are based on the following passage.

    The Arctic Circle comprises approximately 6 percent of the Earth's surface. Of the 21 million square-kilometer Arctic region, only about 8 million square kilometers is onshore; the rest of the area is located on continental shelves, which are covered by no more than 500 meters of water Expeditions to the northern regions of Canada, Russia, and Alaska have discovered some 400 oil and gas fields within the Arctic Circle. These fields are capable of producing upwards of 200 billion barrels of oil and natural gas, a quantity representing about 10 percent of the world's known petroleum reserves. And yet, most of the Arctic Circle region remains unexplored. Some geologists believe that the expansive Arctic continental shelves may contain vast petroleum reserves. 

    Recently, a group of researchers from the United States Geological Survey completed an extensive survey of the Arctic region. The members of the Circum-Arctic Resource Appraisal (CARA) team sought to discover the possible petroleum reserves in all areas north of 66.56 degrees north latitude. Due to the relative lack of information on the Arctic Circle region, the CARA team was unable to employ the standard geological techniques of resource assessment, including discovery prospect modeling and deposit simulation. Instead, the scentiels employed a probabilistic methodology to attempt to pinpoint areas of the Arctic Circle that had at least a 10 percent chance of harboring oil reserves excess of 10 billion barrels. The model used by the researchers determined the probability that a certain location possesses significant oil reserves by considering certain geologic factors typically associated with oil fields, including rock type and formation, and the relative age of the geologic structures. The results of the CARA team's study indicate that 17 of the 25 Arctic Circle regions have a greater than 10 percent chance of holding of reserves. Geologists on the team further conclude that over 70 percent of the estimated oil reserves in the Arctic Circle occur in just five of the regions, while over 70 percent of the probable natural gas reserves lay in just three of the regions. 

The author of the passage is primarily concerns with ....