属于气动薄膜调节阀的有（）。
A、球阀
B、直通单座调节阀
C、笼式阀
D、蝶阀
参考答案：A, B, C, D
— What's your English teacher like?
— ______. [ ]
A. He is good
B. He likes reading
C. He's thirty
D. He's thin and tall
整个热油锅炉的供热系统是一个（）式系统。
A.闭式
B.开式
C.半开半闭
