These days kids grow up so quickly.

如今孩子们成长得真快。

2.in turn 反过来
 

All theories originate from practice and in turn serve practice.

任何理论都来源于实践，反过来为实践服务。

3.have a hunger for 渴望...
 

Most children have a hunger for books.

绝大多数孩子都渴望有书看。