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21. Antarctic _______ we know very little is covered with thick ice all the year round.
A. which
B. where
C. that
D. about which
22. It’s the third time _______ late this month.
A. that you arrived
B. when you arrived
C. that you’ve arrived
D. when you’ve arrived
23. It was in 1969 _______ the American astronaut succeeded in landing on the moon.
A. that
B. which
C. when
D. in which
24. May the fourth is the day ______ we Chinese people will never forget.
A. which
B. when
C. on which
D. about which
25. We are going to spend the Spring Festival in Guangzhou, _______ live my grandparents and some relatives.
A. which
B. that
C. who
D. where
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