四行程发动机每个工作循环各缸的进、排气门各开闭一次。
参考答案：对
亲近社会、服务社会，首先必须自觉履行自己的工作职责，自觉履行宪法和法律规定的公民的基本义务。
--- What did your father say to you just now?
--- He asked me _______________.
A．if had I finished my work
B．that I had finished my work
C．how long had I finished my work
D．whether I had finished my work
