单项选择题

Questions 15 to 17 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. The speaker uses the example of the robot in the space exploration to tell us______.

A.the differences between robots and men
B.the reason why men need to sleep
C.about the need for robots to save power
D.about the danger of men working at night