22. We know a good deal about the people who lived in China 4 000 years ago because they

问题补充：

22. We know a good deal about the people who lived in China 4, 000 years ago, because they write and leave written records for those who lived after them.

A. could

B. should

C. must

D. Shall

答案：

(答案→)A. could

B. should

C. must

D. Shall

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