Tāmen bìxū nǔlì ɡōnɡzuò.

他们必须努力工作。

They have to work hard.

Notes:

他们(tāmen): they

必须(bìxū):must, have to

努力(nǔlì): strive

工作(ɡōnɡzuò): to work

Example:

A:他们必须努力工作。

     Tāmen bìxū nǔlì ɡōnɡzuò.

     They have to work hard.

B:我们也是。

     So do we.

Level: