题目

空间存在竖直向下的匀强电场和水平方向（垂直纸面向里）的匀强磁场，如图所示，已知一离子在电场力和洛仑兹力共同作用下，从静止开始自A点沿曲线ACB运动，到达B点时速度为零，C为运动的最低点.不计重力，则   A.该离子带负电 B.A、B两点位于同一高度 C.C点时离子速度最大 D.离子到达B点后，将沿原曲线返回A点Mr. Smith is an English man. He teaches English well. His English classes are very interesting. He likes us and we like him, too.Mr. Smith has two children—Tom and Mary. Tom is seven and his sister, Mary, is four. Tom goes to school but Mary doesn't. Mr. Smith likes wearing a T-shirt and jeans(牛仔裤). Football is his favorite sport. After school we often have a baseball match. Sometimes Mr. Smith watches and joins us. He plays baseball just for fun. ⑴Mr. Smith is an English teacher.⑵Mr. Smith has one daughter.⑶Mary doesn't go to school because she likes sports.⑷Mr. Smith likes to have sports.⑸We often play baseball with Mr. Smith.