听力对话试题
Questions 23 to 25 are based on theconversation you have just heard.
23.
[A] The effect of the atmosphere onrainfall.
[B] How conditions on earth support life.
[C] How water originated on earth.
[D] A new estimate of the age of earth.
24.
[A] The surface of the ocean is expanding.
[B] Volcanic activity is increasing.
[C] The surface of earth contains tons of cosmicdust.
[D] Thousands of comets are colliding withearth’s atmosphere.
25.
[A] They are found under the oceans.
[B] They were most active when earth wasfirst formed.
[C] Their emissions created earth’satmosphere.
[D] Their fumes are mostly water in thestate of a gas.