扁嘴式喷漆枪两侧的（）出气孔必须保持通气。
A、4个
B、3个
C、2个
D、1个
参考答案：C
Tom didn't go upstairs _____ his mom cleaned up his room.[ ]
A. until
B. from
C. in
D. after
以下哪项不是高血压患者心血管危险分层的内容（）
A.高危
B.极低危
C.中危
D.低危
E.极高危
