问题
选择题
The world's population has grown to more than six times _____ it was in 1800. [ ]
A. which
B. that
C. what
D. the number
答案
答案：C
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The world's population has grown to more than six times _____ it was in 1800. [ ]
A. which
B. that
C. what
D. the number
答案：C
cosωt
