2 sentences

1. 在古代汉语中，名词活用作动词的现象很常见。

   zài gǔ​dài Hàn​yǔ zhōng, míng​cí huó​yòng zuò dòng​cí de xiàn​xiàng hěn cháng​jiàn.

   In ancient Chinese, the phenomenon of nouns being used as verbs is very common.

   Source: Dong Chinese Dictionary

2. 学习知识的关键在于能够灵活运用，做到活用。

   xué​xí zhī​shi de guān​jiàn zài​yú néng​gòu líng​huó yùn​yòng, zuò​dào huó​yòng.

   The key to learning knowledge is being able to apply it flexibly.

   Source: Dong Chinese Dictionary