我对物理学的理解存在很大差距。

There is a big ___gap in my understanding of physics.

我们镇另一个巨大的缺失是缺乏一个游泳池。

Another huge ___gap in our town is the lack of a swimming pool.

报告指出了政策与实践之间的显著差距。

The report identifies a significant ___gap between policy and practice.