增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词；

2）只允许修改10处，多者（从第11处起）不计分。

    Travelled abroad, you should follow the customs of the country where you are visiting. When you invited, it is good manners to refuse or accept an invitation, either by writing or by telephoning. If you go to the patty, it polite to arrive on time. It is good manners to shake hand with your host. You can take a present if you like, possible a bottle of wine，a box of chocolates and some flowers. However, it was not bad manners to take nothing. It is not polite to stay too late before the other guests have gone. Also, it is suggested to or telephone a day or two late to thank your host.

 人类是生活离不开水，某生活污水主要含有碎菜叶、碎塑料薄膜、泥沙、氯化钠和碳酸钠等物质．现欲将其经去渣处理后作为清洗厕所的用水．请问：

（1）捡掉污水中的碎菜叶、碎塑料薄膜等较大的固体后，可对污水进行____操作除去其中捡不掉的固体物质；把生活污水进行处理在利用的目的是____；

（2）①试剂A的化学式是　____ 　，试剂A加入过量的作用是____；

②写出步骤Ⅱ所发生反应的化学方程式　____  ；如果步骤Ⅰ先加入试剂B，步骤Ⅱ加入过量试剂A，也能达到检验氯化钠的目的，理由是____．

用棱长相等的正方体4块，任意摆成一个长方体，可以摆多少种？