我们使用了一个微型摄影机，来观察每天有多少人使用图书馆，而且他们在都做什么。

We used an undercover camera to see how many people used the library and what were they doing.

youdao

我们使用了一个微型摄影机，来观察每天有多少人使用图书馆，而且他们在都做什么。

We used an undercover camera to see how many people used the library and what were they doing.

youdao