In the original testㄛall the animals in a test group are given a substance _______ half of them die.
A. unless
B. until
C. lest
D. provided
查看答案
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
________， 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
微信支付 
支付宝支付