7. The price of maple syrup has jumped from 22 dollars three years ago to 40 dollars a gallon today. It can be concluded that maple-syrup harvesters have been artificially inflating prices and that governmental price regulations are necessary to control rising prices.Which of the following， if ture， casts the most doubt on the conclusion drawn above？

　　（A） The government already requires maple-syrup harvesters to submit their facilities to licensing by the health department. （B） Insect infestation and drought have stunted the growth of syrupproducing maple trees and caused less-abundant syrup harvests.

　　（C） Maple syrup is produced in rural areas that suffer from high unemployment.

　　（D） Technological improvements in maple-syrup harvesting have reduced production costs.

　　（E） Maple-syrup prices have risen many times in the past， though never before at the rate recently observed.

　　8. Artificial seaweed made of plastic has been placed on a section of coast in order to reverse beach erosion. The inventor of the seaweed has concluded that the recent buildup of sand on that section of coast proves that the artificial seaweed reverse beach erosion.Which of the following， if true， would most seriously weaken the inventor's conclusion？

　　（A） The amount of recent sand buildup on that section of coast was less than had been predicted on the basis of the results obtained in controlled experiments.

　　（B） Because artificial seaweed would be buried eventually by additional sand deposits on the coast， more artificial seaweed would need to be put in place every four years.

　　（C） Artificial seaweed of another material which had been previously developed by the inventor failed to add sand to coastline in past trials.

　　（D） The amount of recent sand buildup on that section of coast is the same as the amount of recent sand buildup on otherwise very similar section of coast without artificial seaweed.

　　（E） The amount of recent sand buildup on that section of coast， although considerable， is not yet enough to replace the amount lost during storms on that section of coast in the last twenty years.

　　9. The presence of microorganisms that produce a toxin causes seawater to turn brownish red， phenomenon known as a red tide. Sea otters do not feed in areas where clams， their main source of food， have become contaminated with this toxin. According to a proposed explanation of the otters' behavior， the otters sample the clams in a potential feeding areas and can taste any toxin in them.