Questions 4 to 7 are based on the following conversation. At the end of the conversation, you will be given 20 seconds to answer the questions. Now listen to the conversation. How long is the shaft

A．A British team started to drill southeast from Dover.
B．A French team started to drill northwest from Sangette.
C．The two teams started drilling in 1988.
D．The two teams met under the channel in December 1990.

A．Because of a flood 10,000 years ago.
B．Because of an earthquake 10,000 years ago.
C．Because of a flood 100,000 years ago.
D．Because of all earthquake 100,000 years ago.