如图所示，AB是某个点电荷的一根电场线，在电场线上O点由静止释放一个负电荷，它仅在电场力作用下沿电场线向B运动，下列判断正确的是（ ）
A．电场线由B指向A，该电荷做加速运动，加速度越来越小
B．电场线由B指向A，该电荷做加速运动，其加速度大小变化因题设条件不能确定
C．电场线由A指向B，电荷做匀加速运动
D．电场线由B指向A，电荷做加速运动，加速度越来越大
负电荷由静止向B运动，知所受电场力方向由A指向B，所以电场线的方向由B指向A．场源的电荷的电性未知，无法知道A、B点电场线的疏密，无法比较出电场力，则加速度的大小无法比较．故B正确，A、C、D错误．
故选B．
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| I'm Tom. I'm a student in a middle school. I'm glad to meet you here. First let me say 1 about my family. There are five people in my 2 : my father, my mother, my sister, my cousin brother and I. My father is an 3 worker. My mother is a teacher 4 English. My sister is eighteen and my cousin brother is sixteen. I'm fourteen. We 5 are in the same school. We all study hard. My home is at West Hill. There is a big river near our 6 . Behind it there is a hill. There is one big tree and some small 7 around our house. The big tree is a pear tree and the small trees are apple trees, 8 there aren't any pears or apples on them. 9 a photo of my house. In the photo, you can see three cats in my bedroom. One is white, 10 two are black and white. We like them very much. | ||||
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