Definition: below the surface of the ground Level: B2
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.
