月经周期基本正常,行经时间超过七天以上,甚至淋漓半月方净者,称为()
A.经期延长
B.月水不断
C.月水不绝
D.经事延长
E.以上均是
参考答案:E
已知x=6.61,y=-3.39,求(x-y)(x2+3xy+y2)-5xy(x-y)的值。
The price of the sweaters _____ $20. [ ]
A. is
B. are
C. have
D. has