Red squirrels disappear inside trees, frogs go deep under the mud, and many other animals dig tunnels in the earth. 红松鼠藏到树里面去了，青蛙钻入泥土的深处，而许多其它的动物，则在地里挖坑道。
A tunnel dug to intercept and destroy an enemy's mine. 对抗地道截断或破坏敌人坑道而挖的地道
The tunnel contract to a narrow passageway as you go deep. 再往里走，坑道缩小成了一条窄窄的通道。
The roof of the tunnel was supported by wooden props. 坑道顶用木柱支撑。
