What we don't get here is a sense of whether there really is an alternate secret postal system that serves a sort of underground of private networks.

在这里我们所不明白的是，是否真的存在一个,提供地下的,私密的通信服务的，秘密邮政系统。

耶鲁公开课 - 1945年后的美国小说课程节选

If you're underground, you don't see anything, and buses are really slow.

如果在地下的话，你什么都看不到，而巴士又真的很慢。

喜欢自行车 - SpeakingMax英语口语达人

We didn't know the god was there, and we didn't know he was underground until Milton tells us that he's coming up now.

我们不知道这位神在那儿，直到弥尔顿告诉我们，直到弥尔顿告诉我们我们才知道他隐匿在字里行间,才知道他会出现。

耶鲁公开课 - 弥尔顿课程节选