储气瓶型干粉灭火系统，当采用全淹没灭火系统时，喷头的最大安装高度不大于（）。
A.5m
B.6m
C.7m
D.8m
参考答案：D
分母是5的真分数有______，真分数______1，假分数______1．
—He isn't an excellent astronaut, is he?
—______. [ ]
A. Yes,he isn't
B. No,he is
C. Yes,he is
D. No,he hasn't
