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【单选题】
某研究人员希望分析某种助眠产品对消费者失眠的作用,在对选择的一定规模的消费者进行失眠状况测试后让他们服用了这一产品,然后又进行了同样的测试,结果发现消费者的失眠状况有明显改善。因此,该研究人员认为这款产品对消费者失眠的改善具有一定的帮助。你认为该项研究有效吗?A.
有效
B.
无效
C.
无法判断，因为缺乏对照组的比较
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举一反三
【简答题】Make sure 确保
【单选题】Jenny pushed the door again to ______ it ______.
A.
make sure if; was closed
B.
make sure that; was locked
C.
found out it; was shut
D.
find out that; was open
【单选题】Why did Chanel test her clothes on moving models? a She wanted to make sure they looked good. b She wanted to make sure that models could move around easily. c She wanted to make sure the material was...
A.
a She wanted to make sure they looked good.
B.
b She wanted to make sure that models could move around easily.
C.
c She wanted to make sure the material was strong enough.
【简答题】已知，则的值为 ．已知 ，则 的值为____．
【简答题】已知 ，则 的大小为（ ）；已知 ，则 的大小为（ ）
【单选题】They surveyed the area __ the tomb faced south.
A.
make sure
B.
making sure
C.
to make sure
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