本初子午线是指[ ]
A．赤道
B．日界线
C．0°经线
D．20°W经线
答案：C
John promised his doctor he _____ not smoke and he has never smoked ever since.
A．might
B．should
C．could
D．would
多台水泵并列安装时，间距不得小于( )cm。
A．40
B．60
C．80
D．100
