Definition: a long passage under the ground or through a mountain Level: B1
火车进入了隧道。
The train went into the ___tunnel.
不幸的是，隧道关闭了，所以我们不得不另找路线。
Unfortunately, the ___tunnel was closed, so we had to find another route.
他们在河下建造了一条隧道用于地铁。
They constructed a ___tunnel under the river for the subway.
