3 sentences

1. 我参加了学校运动会的百米赛跑。

   wǒ cān​jiā le xué​xiào yùn​dòng​huì de bǎi mǐ sài​pǎo.

   I participated in the 100-meter dash at the school sports meet.

   Source: Dong Chinese Dictionary

2. 裁判正在为百米赛跑的运动员计时。

   cái​pàn zhèng​zài wèi bǎi mǐ sài​pǎo de yùn​dòng​yuán jì​shí.

   The referee is timing the 100-meter runners.

   Source: Dong Chinese Dictionary

3. 百米赛跑是田径运动中最受关注的项目。

   bǎi mǐ sài​pǎo shì tián​jìng yùn​dòng zhōng zuì shòu guān​zhù de xiàng​mù.

   The 100-meter dash is the most watched event in track and field.

   Source: Dong Chinese Dictionary