题目

A scientist _______ several monkeys in order to study animal psychology. He took a glass bottle, _______ its cork (瓶塞) and put two peanuts inside it. The peanuts dropped to the bottom and were easily seen from the outside. He then passed the bottle to a monkey, who shook it _______ for a long while and was able to get the peanuts when they _______ fell out. The scientist then put some peanuts into the bottle again _______ he had done before and showed the monkey that it only needed to turn the bottle upside down for the peanuts to drop out. _______ the monkey always ignored his _______. Ea点光源照射一个障碍物，在屏上所成的阴影的边缘部分模糊不清，产生的原因是[　　 ] A、光的反射； B、光的折射； C、光的干涉； D、光的衍射。