问题描述：
After they had walked a day in the desert,they ___ all tired out.
A.had been
B.were
C.have been
D.are
选B,请帮我分析一下,谢谢!
A.had been
B.were
C.have been
D.are
选B,请帮我分析一下,谢谢!
问题解答：
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