确知

wǒ què zhī wǒ zhī qián jiàn guo tā

我确知我之前见过她。

I know for certain that I have seen her before.

wǒ què zhī wǒ wèi shén me yào zuò tè dìng de yī xiàng gōng zuò

我确知我为什么要做特定的一项工作。

I have to know exactly why it is I'm doing a particular job.