The two subjects are closely connected.

　　這兩門學科緊密相連。

　　Those two processes are very closely interlinked.

　　那兩種工藝非常緊密地互相關(guān)聯(lián)。

　　Their political careers had become closely intertwined.

　　他們的政治生涯已經(jīng)緊密地結(jié)合在一起了。