将重为3N的小球放入装有水的容器甲中，静止时的状态如图所示，则小球所受浮力的大小为____N．小球的体积为____m³；若向水中加人足量的盐，小球将____（选填“上浮”“悬浮”或“下沉．）．（g取1ON/kg）

短文填空先通读下面的短文，然后根据短文内容和所给首字母，在空格内填入一个适当的词，使短文意思完整。
      American people like to say “Thank you” when others help them or say something kind to them. People of many other countries do so, too. It is a very good habit.
      You should say “Thank you” when someone p____  you the salt on the table, when someone walking before you k____  the door open for you, when someone s____  you have done your work well, or you have b____  a nice thing, or your city is very beautiful. “Thank you”is used not only between friends, but also between parents and children, brother and sisters, husbands and wives.
    “Excuse me”is another s____  sentence they use. When you hear someone say so behind you, you know that someone wants to walk p____ you. It is not polite to b____  others while they are talking. If you want to speak to one of them, say “Excuse me” first, and then begin talking. You should also do so when you want to cough(咳嗽) or make any u____  noise before others.

下面的式子中，表示x与y互为倒数的算式是（  ）