29. About one in ten computer game players show signs of addictive behavior that      have
negative effects on their family, friends and school work , according to a new study.

Jim has many hobbies, ________ swimming, hiking and playing badminton.

My aunt works ________ a newspaper _______ a reporter.

细胞中既具有双层膜结构，又能让蛋白质等大分子通过的膜结构是（    ）

如图6所示，空间存在相互垂直的匀强电场和匀强磁场，电场的方向竖直向下，磁场方向垂直纸面向里，一带电油滴P恰好处于静止状态，则下列说法正确的是(　　)