题干

如图,矩形的两条对角线的一个交角为60°,两条对角线的长度的和为20cm,则这个矩形的一条较短边的长度为(  )

A:10cm

B:8cm 

C:6cm

D:5cm

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答案(点此获取答案解析)

D

同类题2

阅读下面短文,从各题所给的A、B、C、D四个选项中选出最佳选项。
C
    It was Sunday. Henry did some shopping and then went to the car park. It was about to start the car when a robber stood up from the back seal. He held a knife to Henry's bead. "Give mc your wallet and drive me to North Street!" he shouted.
    "All right," Henry answered. Then he started the car and drove away. Being 72 years old, be knew he could not fight the young robber. He knew he needed help. Where were the police? As he drove towards each crossing, he looked up and down the side streets, hoping to meet a police car. But he could see none. "Just my luck," he thought. "If I was driving too fast, there would be a police car on every corner."
    So he pushed his foot down on the accelerator (油门), and the car ran much faster. "What are you doing?" shouted the robber. "Keeping off the police," Henry answered. "I thought I saw a police car back there."
    He ran red lights, drove the wrong way on one-way streets. On two way streets he drove on the wrong side of the road. Not one policeman saw him. Again Henry's plan was not working. He had to try a new plan.
    He turned a corner and saw the police station in front. Then he drove his car as fast as he could towards the police gate. The car hit a police motorbike down and stopped. Henry shouted, "Help! Help!" Then he turned back to grab the man's knife. At the same time the policemen heard the shout and quickly caught the robber.