常用的松键联结有（）联结两种。
A．导向平键和钩头楔键
B．普通平键和普通楔键
C．滑键和切向键
D．平键和半圆键
E．楔键和切向键
参考答案：D
I hope there are enough glasses for each guest to have____ .
A．it
B．those
C．them
D．one
