Though I’ve tried very hard to improve my English, by no means ___________with my progress.

A．the teacher is not satisfied

B．is the teacher not satisfied　　

C．the teacher is satisfied

D．is the teacher satisfied

为便于管理与维修，车间压缩空气管路应以沿墙或柱子架空敷设为主，架空敷设高度以
不妨碍交通为原则，但一般不小于（），并尽量减少对采光的影响。

A．2.5m

B．3.5m

C．4.5m

D．5.5m