21.
A. Record details of space exploration.
B. Monitor the change of lunar weather.
C. Study the effect of radiation and vacuum on its materials.
D. Explore the possibility of human settlement on the moon.
Questions 22 to 25 are based on the passage you have just heard.22.
A. It is likely to remain a means of business communication.
B. It is likely to be a competitor of various messaging apps.
C. It will gradually be replaced by social media.
D. It will have to be governed by specific rules.
23.
A. Save the message in their file.
B. Make a timely response.
C. Examine the information carefully.
D. See if any action needs to be taken.
24.
A. It is to be passed on.
B. It is mostly junk.
C. It requires no reply.
D. It causes no concern.
25.
A. Make it as short as possible.
B. Use simple and clear language.
C. Adopt an informal style of writing.
D. Avoid using capitals for emphasis.
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