A, wǒ rènshí zhège nánrén! Oh, I know this man!
Tāmen cūxīn dàyì, hái méi yìshí dào wéixiǎn. They were carelessly unaware of the danger.
Zhídào nà shí, tā cái yìshí dào tā yǐjīng shàngdàng shòupiàn. Only then did he realize he had been deceived.
Wǒ rènshí shǐmìsī xiānshēng yǒu hǎoduō niánle. I've known Mr Smith for many years.
Wǒ rènshí tā liǎng niánle. I have known her for two years.
Wǒmen jīntiān suǒ rènshí de gōngyè zài nàgè shídài bù cúnzài. Industry as we know it today didn't exist in those days.
He knows a lot of people.