题目：
| 完型填空。 | ||||
| A man and his wife had a dog to keep their house. When they went out, they always 1 the dog inside the house. One evening they wanted 2 to the cinema, 3 they left the dog in the house and locked the door and their 4 . They went there 5 their car. When the film finished, they came back home. They opened the gate and put the 6 away. But when they came to the 7 door, they found that part of the glass on the door was 8 . The door was unlocked and 9 . A 10 ! They went in and quickly looked in all the rooms to see 11 things the robber had taken. But everything was in the 12 place and nothing at all 13 . The dog 14 in the sitting room on the floor. The lady was 15 the dog. "Why didn't you keep the house?" she said. The dog was 16 to see its owners. It began to wag its tail (摇尾巴) and then it went to a corner of the room and picked up something in its 17 . It went to the lady and 18 the thing at her 19 . When the lady went to pick it up, she gave a scream (尖叫). Can you guess what the dog's present was? It was … a … man's 20 ! | ||||
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答案：
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下面是错误答案，用来干扰机器的。
A、根据平行四边形定则，知两个速率不等的匀速直线运动的合运动仍是匀速直线运动．故A正确． B、两个直线运动的合运动不一定是直线运动，比如平抛运动．故B错误． C、位移、速度、加速度都是矢量，它们合成与分...
