给水泥罐充气时开关闸门的顺序是什么?
参考答案:给水泥罐充气时开关闸门的顺序是先关闭放空闸门,再打开进气闸门。
I don't think your sister has finished her French course, ______? [ ]
A. don't I
B. do I
C. hasn't she
D. has she
合成材料的使用给人们带来了方便,但是它们的废弃物也带来了环境问题,特别是废弃塑料带来的,废弃塑料的回收和利用显得非常重要。下列属于塑料制品回收标志的是 [ ]
A.
B.
C.
D.