题目内容

液压传动系统中，常用的方向控制阀是()

A.减压阀
B.调速阀
C.单向阀
D.换向阀

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液压传动系统中，常用的的压力控制阀是()

A.调速阀
B.溢流阀
C.减压阀
D.顺序阀

It could be inferred from the text that Pangu lived for ________ years .

A. 3000
B. 18000
C. 5000
D. 400000

After Pangu’s death, his body turned into _______ on earth.

A. trees
B. pillars
C. animals
D. mountains

All of the following are the problems after the collapse of the four corners of the sky except ____________.

A. big fires
B. violent animals
C. frequent earthquakes
D. crazy floods