Some university students are going to France in summer holidays, and some (are going) to America.

在并列句中，如果后一分句与前一分句中的谓语动词重复，常省略谓语动词或谓语的一部分，但介词不能省略，避免引起歧义。

My brother is a doctor while my sister (is) a teacher. 我哥哥是位医生，而我妹妹是位教师。

I work in a factory and my brother (works) on a farm. 我在工厂上班，我哥哥在农场劳动。

My parents live in the countryside, but I (live) in the city. 我父母住在乡下，而我住在城里。