问题
单项选择题
目前汽车上的停车辅助系统（倒车雷达）一般都是利用（）的反射原理，在低速倒车时检测驾驶人用眼睛无法监视的死角地带的障碍物，距离过近时以警告音方式警告驾驶人，避免发生碰撞事故。
A．红外线
B．超声波
C．直接检测
答案
参考答案：B
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目前汽车上的停车辅助系统（倒车雷达）一般都是利用（）的反射原理，在低速倒车时检测驾驶人用眼睛无法监视的死角地带的障碍物，距离过近时以警告音方式警告驾驶人，避免发生碰撞事故。
A．红外线
B．超声波
C．直接检测
参考答案：B
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| My name is Bill. I 1 a sister. Her name is Katty. 2 is her birthday. She is twelve, and she 3 cakes very much, so my father and mother 4 her a big cake. Look! The cake is 5 the table of her bedroom. It's her lovely cake. You can see her 6 and some flowers on it. There are 7 things for her birthday. 8 are apples, pears, bananas and some toys. I 9 her a new book as a present. Her good friends Kate, Lily and Lucy are coming (就要来了). She would like to eat the birthday cake 10 her friends. | ||||
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