下列动物中,名字中都有一个“鱼”字，但属于真正的鱼类的是（    ）

青少年时期应该注意青春期的____ 健康和____ 健康．

某同学研究平直路面上自行车的运动，以下是他的处理方法，其中属于理想化的是（   ）

    These days, many students like playing 3D games. Do you know what 3D games are like? In most 3D games, game players need to control (控制) a character. The character can be a robot or a soldier (士兵). Game players usually use the mouse to make the character move around in his own world. Game players can find things such as food and weapons (武器) to help them go on with the game. The character can go straight, sit down, turn left, turn right or pick up things in the game.
    Some 3D games have many levels (等级). The character needs to finish different goals for each level.Game players can play against their computers, and sometimes they can play with other players on-line. It's great fun to play 3D games. But playing 3D games for long is not good for our study.

如图示为某电容传声器结构示意图，当人对着传声器讲话时，膜片会振动．若某次膜片振动时，膜片与极板距离减小，则在此过程中（　　）