3 sentences

1. 单体通过聚合反应形成聚合物。

   dān​tǐ tōng​guò jù​hé fǎn​yìng xíng​chéng jù​hé​wù.

   Monomers form polymers through polymerization.

   Source: Dong Chinese Dictionary

2. 这种单体在特定条件下会发生聚合反应。

   zhè zhǒng dān​tǐ zài tè​dìng tiáo​jiàn xià huì fā​shēng jù​hé fǎn​yìng.

   This monomer undergoes polymerization under specific conditions.

   Source: Dong Chinese Dictionary

3. 许多小溪流聚合在一起，形成了一条大河。

   xǔ​duō xiǎo xī​liú jù​hé zài yī​qǐ, xíng​chéng le yī tiáo dà​hé.

   Many small streams joined together to form a large river.

   Source: Dong Chinese Dictionary