结肠癌
A．CEAB．p-ANCAC．c-ANCAD．ASC
参考答案：A
从多边形的一个顶点共引了6条对角线，那么这个多边形的边数是______．
He wrote a letter ________ he explained what had happened in the accident.
A．what
B．which
C．where
D．as
