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问题 多选题
如图所示，光滑的水平面上，小球m在拉力F的作用下做匀速圆周运动，若小球到达B点时F突然发生变化，下列关于小球的运动的说法正确的是（　　）

A．F突然消失，小球将沿轨迹Ba做离心运动

B．F突然变小，小球将沿轨迹Ba做离心运动

C．F突然变大，小球将沿轨迹Bc做向心运动

D．F突然变小，小球将沿轨迹Bb做离心运动

答案

ACD

阅读理解

My name is Mary. I’m a student. I’m twelve. My father is a policeman. My mother is a nurse. Nick is my brother. We are all at home today, because today is Sunday. My brother Nick is a student, too. We are in the same school. There are thirty-five classes in our school. My classroom is very big.

小题1:_______are students and in the same school.

A．My sister and I

B．My brother and I

C．My brother and my sister

D．Andy and I小题2:What’s Mary’s mother?

A．She is a teacher.

B．She is a student.

C．She is a nurse.

D．She is a doctor.小题3:There are _______ classes in Mary’s school.

A．25

B．35

C．24

D．34小题4:How old is Mary?  ________.

A．12

B．14

C．13

D．30小题5:Mary’s classroom is _______.

A．not big

B．not very small

C．not strong

D．not short
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判断题

把42缩小1000倍，小数点向左移动三位。[ ]
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