单项选择题


Questions 17—20 are based on the following monologue about hobbies. You now have 20 seconds to read Questions 17—20.
What is one of the reasons for the speaker to switch his interest to underwater exploration

A.The ocean is frienghtening.
B.Underwater exploration is so much cheaper than space flight.
C.He wants to make more money.
D.The space is more philosophical.