We should go to school at 8:00 _____ school mornings. [ ]
A. at
B. in
C. on
D. of
答案:C
组成公理化系统的一般程序?
涂料用量少,颜色更换频繁的场合应选用()喷枪
A、吸上式
B、重力式
C、压送式