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單項(xiàng)選擇題

Most marine biological sewage treatment plants consist of all the following statements except （）.

A.aeration tanks
B.settling tanks
C.disinfection agent
D.anaerobic bacteria

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單項(xiàng)選擇題

To prevent accidents from occurring, special valve chests are used in such cases in which interchangeable blanks and connecting passages are incorporatedThe bold and italic word “which” means （）.

A.accidents
B.special valve chests
C.interchangeable blanks
D.connecting passages

單項(xiàng)選擇題

A check valve is another name for （）.

A.a test valve
B.an inspection valve
C.a stop valve
D.a non-return valve