齐桓公确立霸主地位的主要方式是[ ]
A.管仲改革
B.尊王攘夷
C.组织会盟
D.问鼎中原
答案:C
The reason why he was late was ___he had taken a wrong bus.
A.because
B.whether
C.because of
D.that
举例说明什么是语言变体。