蒸发量大于0.5t/h的锅炉,其安全阀的数量应为()。
A. 1个
B. 至少1个
C. 至少2个
D. 仅省煤器上安装即可
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最理想的流水施工组织方式是()。
A. 等节奏流水施工
B. 异节奏流水施
C. 无节奏流水施
D. 分别流水施工
This is one of the highest buildings that ______ in our city.
A. are ever built
B. have ever built
C. have ever been built
D. were ever built
Gelert was ______.
A. a cat
B. a wolf
C. the Prinee's enemy
D. a dog
By the time you came back yesterday, they ______ for London.
A. have left
B. left
C. had left
D. leave