Even with the new development in research， only a tiny ________ of all tests are done without using animals.
A. variety
B. amount
C. plenty
D. proportion
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________， what could we do？
A. Should it rain tomorrow
B. Tomorrow it should rain
C. If it rains tomorrow
D. If it will rain tomorrow
The Netherlands is the only country in Europe which permits euthanasia， ________ it is not technically legal there.
A. if
B. otherwise
C. although
D. unless
煤尘爆炸的下限浓度是()。
A. 45mg/m3
B. 45g/m3
C. 2000mg/m3
曹操与王允见面后关于落座几次的推让是一种礼仪的表现，但背后暗藏的是一种相互试探。()
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