现有以下四种物质：

A．新制的氢氧化铜Cu（OH）₂悬浊液B．晶体硅Si

C．明矾KAl（SO₄）₂•12H₂OD．过氧化钠Na₂O₂

请你根据题意，选择恰当的选项用字母代号填空．

（1）检验尿液中是否含有葡萄糖，可使用 ____；

（2）要使含少量泥沙的浑浊水变澄清，可使用 ____；

（3）常盛放在呼吸面具里的物质，可使用　 ____　；

（4）用于制造计算机芯片的材料，可使用 ____　．

印度由于……很不稳定，最容易发生的自然灾害是（    ）

根据短文内容，判断正误。

      When you're invited to have dinner at a foreigner's home, please remember the followings.

      At the table, when the hostess(女主人) picks up her napkin, you may pick up yours and put it on your legs.

      If a servant(佣人) passes food around, he will pass the dish to you at your left hand so that you can easily serve yourself with your right hand. Never serve yourself while the dish is on your right. It is then the turn of your neighbour on the right.

      Do not reach across the table to get something in front of someone. That is not polite. Ask him or her to pass it to you.

      There are things in the middle of the table, such as bread, butter, and candies. You shouldn’t take any until the hostess tells the servant to pass them to you.

      Do not leave your seat without saying anything. If you need to leave the table to go to the washroom or do something else, you should say “Excuse me for a moment, please.”