问题
解答题
平行四边行的一个角为直角，则它一定是（ ）
A．长方形
B．正方形
C．梯形上
D．无法判断
答案
根据长方形和平行四边形的特征，平行四边形有一个角是直角就一定是长方形；
故选：A．
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平行四边行的一个角为直角，则它一定是（ ）
A．长方形
B．正方形
C．梯形上
D．无法判断
根据长方形和平行四边形的特征，平行四边形有一个角是直角就一定是长方形；
故选：A．
Helen Keller was a very bright, beautiful girl. the age of six months she could already say a few words. But unluckily, before she was two years old, she was badly . After that, she could not see or hear, and soon she could not even . Since then Helen had to fight（斗争） for what she wanted. When she was six, her parents invited a teacher for her. the help of the teacher, she began to see and hear the world around her .Through her . She learned to the books for the blind. The teacher took Helen for long walks, and her about all the beautiful sights. Helen touched flowers, climbed the trees and smelled a rain storm(暴风雨) before it came. She also learned how to swim and ride a horse. After she , she became a famous writer in America .Her first and most famous book is The Story of My Life. Her story has brought new to many blind and deaf people. It has given light to those in darkness and encouraged to live and work.
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