3 sentences

1. 小心别中了他的套子。

   xiǎo​xīn bié zhòng le tā de tào​zi.

   Be careful not to fall into his trap.

   Source: Dong Chinese Dictionary

2. 他给手机买了一个粉色的套子。

   tā gěi shǒu​jī mǎi le yī gè fěn​sè de tào​zi.

   He bought a pink case for his phone.

   Source: Dong Chinese Dictionary

3. 发生性关系时一定要戴套子，以免意外怀孕。

   fā​shēng xìng guān​xi shí yī​dìng yào dài tào​zi, yǐ​miǎn yì​wài huái​yùn.

   It is important to wear a condom during sex to prevent unintended pregnancy.

   Source: Dong Chinese Dictionary