3 sentences

1. 他原本正在自行调查。

   tā yuán​běn zhèng​zài zì​xíng diào​chá.

   He was carrying out his own investigation.

   Source: OpenSubtitles

2. 这个问题请自行处理。

   zhè​gè wèn​tí qǐng zì​xíng chǔ​lǐ.

   Please handle this matter on your own.

   Source: Dong Chinese Dictionary

3. 难怪有些学生会自行解决问题。

   nán​guài yǒu xiē xué​sheng huì zì​xíng jiě​jué wèn​tí.

   No wonder some students take matters into their own hands.

   Source: OpenSubtitles