We live in the computer age. People use computers to do much of their work. But few people know how to look after them. Remember the following when you use your computer:

1.Keep your computer in a cool, dry room. Too much or too little heat is bad for computers. Damp(潮湿) is also bad for them.

2.Do not let people smoke near your computer. Smoke of all kinds is very bad for many parts of a computer.

3.Do not eat or drink when you are near your computer. Pieces of food and a little water in the keyboard are also bad for a computer.

4.Keep your screen clean and do not have it too bright. They are bad for your eyes. Make sure the screen is not too far from or too near your eyes. Some people use different glasses to protect their eyes when they use a computer.

小题1:Computers can          people to do a lot of work.

A．use

B．help

C．make

D．take小题2:Few people know how to          their computers.

A．look at

B．try out

C．look for

D．take care of小题3:A computer works well at a temperature of         .

A．0℃

B．-5℃

C．20℃

D．35℃小题4:Smoke is not good for many parts of a computer, is it?

A．Yes,it is.

B．No,it isn't.

C．Yes,a little.

D．Not at all.小题5:A dirty screen or a very bright screen is    for your eyes.

A．bad

B．good

C．useful

D．helpful

菠菜营养丰富，长期以来民间流传着“菠菜不能与豆腐同食”的说法。某学校化学兴趣小组的同学拟通过实验探究：菠菜是否含有草酸类物质？草酸又有哪些性质？通过上网查询，获得以下资料：草酸又名乙二酸，其酸性比乙酸稍强，草酸及其盐具有较强的还原性，草酸晶体(H₂C₂O₄·2H₂O)的熔点为100.1℃，在175℃时受热分解，草酸钙是难溶于水的白色固体。

他们设计的实验步骤如下：

1．将菠菜在少量开水中煮沸2～3 min，冷却后滤去菠菜，得滤液(含有少量CO₃^2—杂质)。向滤液中加入足量Ca(OH)₂溶液，然后再加入足量CH₃COOH溶液，观察现象。

2．用草酸晶体(H₂C₂O₄·2H₂O)做以下实验：

请回答以下问题：

(1)步骤1中加入CH₃COOH溶液的作用：___________________

(2)A处应选择________(填“Ⅰ”或“Ⅱ”)，在做实验之前，应先____________________。

(3)实验2过程中观察到C、E装置中的溶液均变浑浊，且D装置中黑色粉末变为红色，写出A中草酸晶体(H₂C₂O₄·2H₂O)发生反应的化学方程式：______________，装置B的作用是___________________。

(4)为使实验结论更加严密和安全，在以上所连接的装置C、D间还需依次添加装有________、________、________(液体试剂)的洗气瓶，此外指出上述装置中的不足之处还有________。