自考《英语(一)》试题练习:介词的用法(3.3)
单选题
[2005.4]In one type of laboratory test all the variables ________one are controlled.
A.by
B.and
C.but
D.or
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单选题
[2005.4]In one type of laboratory test all the variables ________one are controlled.
A.by
B.and
C.but
D.or