3 sentences

1. 我想不到她留他们活口的理由。

   wǒ xiǎng bù dào tā liú tā​men huó​kǒu de lǐ​yóu.

   I can't think of a reason she'd keep them alive.

   Source: OpenSubtitles

2. 凶手为了不留活口，残忍地杀害了所有的目击者。

   xiōng​shǒu wèi​le bù liú huó​kǒu, cán​rěn de shā​hài le suǒ​yǒu de mù​jī​zhě.

   To leave no witnesses, the killer brutally murdered all of the onlookers.

   Source: Dong Chinese Dictionary

3. 侦察小队在昨晚的伏击中抓到了一个活口。

   zhēn​chá xiǎo​duì zài zuó​wǎn de fú​jī zhōng zhuā​dào le yī gè huó​kǒu.

   The reconnaissance squad captured a live prisoner in last night's ambush.

   Source: Dong Chinese Dictionary