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【单选题】
Our information about the population of the earth before the first century after Christ comes mainly from ______.A.
estimates based on current population growth
B.
references in literature and mythology
C.
estimates based on previous population growth
D.
written records and cultural remains
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【单选题】He aske d ______ for the violin .
A.
did I pay how much
B.
I paid how much
C.
how much did I paid
D.
how much I paid
【单选题】Students are asked to prepare material in advance of each weekly ________.
A.
course
B.
meeting
C.
seminar
D.
Gathering
【简答题】约束是指在机械结构中起________作用的位移型边界条件,这种边界条件是机械结构________的客观描述。