题目

阅读下面短文，根据短文内容回答下列各题。 （A）Helen Keller was born in 1880 in USA．She was a great woman． When Helen was a baby, she got very sick．After many weeks, the doctor said, She is better, but she can't see or hear． Her mother and father were very sad． After a few year, things got worse, there was no way for Helen to speak to others．She heard nothing．（B）She didn't understand anything． Then one day a teacher came to live with Helen and her family．The teacher helped Helen learn about words．Helen was a very clever girl and soon she learned to 下列说法正确的是 [     ]A.3x2y与3xy2是同类项B.3xy与-2yx不是同类项C.-|-a|一定是负数D.如果ab<0，则a，b异号