下列计算正确的是[ ]
A．a2a3=a6
B．a6a3=a2
C．（a2）3=a6
D．（a+2）（a﹣2）=a2﹣2
答案：C
There _______ lots of foreign visitors in Beijing in 2008. [ ]
A. is
B. are
C. be
D. will be
脐静脉穿刺导致的胎儿早期丢失，发生率为
A．3%
B．<0．5%
C．1%
D．2%
E．5%
