微笑时唇高线位于上颌中切牙的（）
A.切缘
B.切1／3
C.切1／2
D.切2／3
参考答案：D
I have ______ friends at school. I like playing with ______. [ ]
A. much; they
B. many; them
C. a lot of; their
D. lots of; theirs
一般情况下数组a(3,4,5)包含的元素个数为( )。
A．345
B．12
C．120
D．60
