Questions 23 to 25 are based on the conversation you have just heard.

A. Because the water pressure is greater than air pressure.
B. Because the first Comets crashed in the water.
C. Because there is less damage when the explosion takes place under water.
D. Because it is the only way available for engineers to find out which part has cracked.

A. They smile to cover embarrassment.
B. It is an unusual and even suspicious behavior.
C. They smile to show politeness.
D. It is an expression of pleasure.