他的钥匙掉进池塘后沉到了水底。

His keys ___sank to the bottom of the pond after falling in.

这家公司的声誉因为丑闻而大幅下滑。

The company's reputation has ___sunk because of the scandal.

他把所有积蓄都投进了这家新公司，现在后悔了。

He regrets having ___sunk all his money into this new business.

他全神贯注于自己的研究中，完全没注意到时间的流逝。

He was so ___engrossed in his research that he didn't notice the time passing.