have been at的用法和樣例：
例句
- I have been at sea for four lousy weeks in this tub.
我已經乘這條老爺船在海上航行了四個倒霉的星期。 - All her clothes have been at pawn.
她所有的衣服都已典當了。 - Look at the time! We shall have been at the theatre ten minutes ago.
瞧都什麽時候了！十分鐘前我們就該到戲院了。 - If the lights were on, they must have been at home.
如果燈亮著，那麼他們一定在家
