下颌尖牙间宽度在几岁后就几乎不再增加（）
A.3岁后
B.5岁后
C.7岁后
D.9岁后
E.11岁后
参考答案：E
已知复数z1=m+2i，z2=2+i，若z1•z2为纯虚数，则实数m的值为（ ）
A．1
B．-1
C．4
D．-4
In the recent G20 Summit, President Hu seriously get the statement ______ to the world _______
European countries should rely on themselves to overcome the crisis.[ ]
A．across, whether
B．over, whether
C．around, what
D．across, that
