判断．

把一个分数约分后，分数的大小和分数单位都不变．

以下是探究Fe、Cu、Ag三种金属活动性的实验。

①A中观察到铁丝表面____；

②B中发生反应的化学方程式为____，该实验过程中可观察到的现象有____

a.冒气泡  

b.出现海绵状银白色固体 

c.铜丝表面变黑 

d.无色溶液变为蓝色

③为达到实验目的，还需补充一个实验（写成所需试剂化学式）____。

贾某在外地一家公司上班，但是这段时间公司总是找理由不给贾某发工资。在维权过程中，贾某应该明确（    ）

如图所示的实验，是我们在学习分子动理论时做过的一些实验：

图a：浓硫酸铜溶液与清水开始界面十分清晰，几天之后，两种液体混合均匀了；

图b：玻璃板的下表面接触水面，发现拉力大于玻璃板的重力；

图c：水和酒精充分混合后的总体积小于混合前水和酒精的总体积；

图d：将红墨水滴入水中，可以看到它在水中扩散开来；

图e：将两个底面干净、平整的铅块紧压在一起，两个铅块就会结合在一起，下面吊一个较重的物体也不会将它们拉开．

        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 online. It’s great fun to play 3D games. But playing 3D games for long is not good for our study.