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问题 选择题

下列叙述正确的是  [ ]

A．稀释浓硫酸时应将水倒入浓硫酸中，并用玻璃棒不断搅拌

B．浓硫酸敞口放置一段时间后，质量分数会变小    

C．浓硫酸是常用的干燥剂，可以干燥氨气等气体    

D．将100g溶质质量分数为98%的浓硫酸稀释为49%，需加水50g

答案

答案：B

完形填空

改写后的课文内容填空（共10个空，每空1分，满分10分）（给出首字母）

Li Daiyu and her cousin Liu Qian were on a trip to Canada to visit their cousins. They decided to catch the train, The True North, to cross the whole c______.

They began their journey in Vancouver, a city s______ by mountains and the Pacific Ocean. A______ the train, the cousins settled down in their seats. When they crossed the Rocky Mountains, they managed to catch s______ of some mountain goats and even a grizzly bear and an eagle. In Calgary, they learned that cowboys, most of whom had a g______ for riding horses, came from all over the world to compete there in the Stampede.

After two days’ travel, the girls began to realize that Canada is quite e______. At school, they had learned that most Canadians live within a few hundred kilometers of the USA b______, and that Canada’s population is only s______ over thirty million, but still they were a______ to see such a large country with so small a population.

That night as they slept, the train rushed southward towards Toronto, the biggest and most w______ city in Canada.
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单项选择题

戊肝疫苗属（）疫苗。

A、减毒活疫苗

B、多糖疫苗

C、基因工程疫苗

D、治疗性疫苗
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