若方程x2-nx=7+n的一个根是2，则n=______．
∵方程x2-nx=7+n的一个根是2，∴4-2n=7+n，解得n=-1．
It's high time that we _____ measures to stop selling polluted vegetables. [ ]
A. must take
B. take
C. took
D. will take
以下哪些瘿病在中药治疗无效时应该考虑手术治疗（）
A.气瘿
B.肉瘿
C.瘿痈
D.石瘿
E.瘿瘤
