一些动物，比如鼹鼠，生活在地下。

Some animals, such as moles, live ___underground.

我们探索了一条通向古老房间的地下通道。

We explored an ___underground passage that led to an ancient chamber.

为了躲避当局，他转入地下并藏身在一个偏远的地方。

To escape the authorities, he went ___underground and hid in a remote location.