题干
——The little girl often has nothing for breakfast, ________she?
——_______. Because she often gets up late and is afraid of being late for school.
A：has; Yes
B：doesn't; No
C：does; No
D：hasn't; Yes
答案(点此获取答案解析）
C
场方向射入带电平行板的匀强电场.离子飞出电场后的动能为Ek，当在平行金属板间再加入一个垂直纸面向内的的匀强磁场后，离子飞出电场后的动能为Ek/,磁场力做功为W，则下面各判断正确的是（ ）