题目

Life in the Clear    Transparent animals let light pass through their bodies the same way light passes through a window. These animals typically live between the surface of the ocean and a depth of about 3,300 feet—as far as most light can reach. Most of them are extremely delicate and can be damaged by a simple touch. Sonke Johnsen, a scientist in biology, says, “These animals live through their life alone. They never touch anything unless they’re eating it, or unless something is eating them.”    And they are as clear as glass. How does an animal become see-through? It在手电筒电路中，提供电能的是A．开关B．灯泡C．导线D．电池