问题
多项选择题
配制甲烷校准气样的装备和方法必须符合国家有关标准，选用纯度不低于（）％的甲烷标准气体作原料气。配制好的甲烷校准气体不确定度应当小于（）％。
A.99.9
B.99.5
C.3
D.5
答案
参考答案：A, D
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配制甲烷校准气样的装备和方法必须符合国家有关标准，选用纯度不低于（）％的甲烷标准气体作原料气。配制好的甲烷校准气体不确定度应当小于（）％。
A.99.9
B.99.5
C.3
D.5
参考答案：A, D
Directions: For each blank in the following passage there are four words or phrases marked A, B, C and D .Fill in each blank with the word or phrase that best fits the context. Would you send a monkey to do your shopping for you? Sounds very strange, doesn’t it ? But monkeys can be trained to do some wonderful things. Most people know that monkeys are one of 36 cleverest beasts(兽). Scientists have been studying the connection（联系） __37__ monkeys and people for a long time. They have done experiments that test __38__monkeys are able to do simple things. In one test, a scientist put two monkeys in two cages beside each other. Each cage had a machine. One cage had a machine which gave out water. __39__ had one which gave out food. Each monkey was given _40__ black and white coins. The black coins worked _41_ in the food machine. The white coins worked in the machine with the __42__. After some time, both animals _43__ know which coin worked in which machine. Then the test was made _44__. The coin s were taken away. The monkey with the water machine was __45_ to have any water for twenty-four hours. The food monkey was prevented from __46_ any food. The next day, the coins were returned to the monkeys. This time, __47__, the monkey with the food machine was given coins for water machine, and the monkey with the water machine was given the coins that worked in the food machine. What did the two __48__ monkeys do? The two clever monkeys __49__ through the bars (栅栏) of their cages and __50_coins with each other.
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