They are not all accounted for有的已经失踪不知去向

account for:报账;说明(原因等)； 对 ... 负责

He could not account for his absence from school.

他无法说明他旷课的原因。

He'll have to account for where every cent goes.

他得说明所花掉的每一分钱的用途。

He has been asked to account for his conduct.

他被要求解释他的行为。

account的用法:

1.on his own account和of his own accord不可混用，前者意为“为了自己的利益地，自己负责地”，后者意为“自愿地，自发地”；

2.on account of，意为“因为”，现比较少用upon去替代on；

3.account后可接宾语和表语，且在宾语后偶尔会加上to be,偶尔会加上as，但都不常用。

I account him wise.

I account him a wise man.

注意句子On no account（决不）should we neglect our work中用的是should we,不是we should。

常用短语:

on account记帐

on no account决不

You know of what I speak,你知道我在说的是什么吗?

know of:知道, 听说

Do you know of any restaurants open now?

你知道现在那里还有餐厅是营业的吗？

I don't know of anything to prevent you from doing so.

我不知道有什么能阻止你这样做。