Questions 18 to 20 are based on the following passage. At the end of the passage, you will be given 15 seconds to answer the questions. Now listen to the passage. Why do XXXX-making beds need protection from the sun’s rays
A．They are active during daylight hours. B．Their heads are exposed to sunlight while they sleep. C．They have only partially adapted to their tropical environment. D．Their wings are easily damaged by ultraviolet radiation.