Beijing is the capital city of ___________.[ ]
A. China
B. Australia
答案：A
可消除检测体系或样本混浊的方法是单试剂双波长法。()
I went to see you last Saturday, _____there _____no one in the room.[ ]
A. but; was
B. but; is
C. and; was
D. and; were
