波士顿矩阵的应用中"明星"业务，处于第（）象限。
A.一
B.二
C.三
D.四
参考答案：B
He isn’t very successful ________a singer but he is quite known ________his music.
A．for;as
B．as;to
C．as;for
D．for;to
上颌第二前磨牙单根管者约为（）
A.5%
B.20%
C.40%
D.50%
E.80%
