氨制冷系统安装时，蒸发排管扽180°弯头可以使用两个90°压制弯头焊接替代。
参考答案：错
I bought a dress for only 10 dollars in a sale; it was a real ______.[ ]
A. exchange
B. bargain
C. trade
D. business
因式分m2-4n2=______．
