如果对提出来的问题确实不了解、不知道，可以说老实话，必要时事后提供书面的答复。

If you have no idea how to answer the question, say you don't know and, if necessary, promise to provide a written response afterwards.

youdao

此时您可能并不知道自己对哪些东西不了解。

At this point, you probably don't know what you don't know.

youdao

我对贵重物品不了解，所以也不知道它值不值。

I don't know about this expensive stuff, so I don't know whether it's worth it or not.

youdao

I don't know how much you've seen, but quite often the way you learned physics earlier on in high school is probably different from the way professional physicists think about it.

我不知道你们对物理有多少了解,但你们以前在高中所学的物理知识,和资深物理学家们的看法,常常是很不一样的

耶鲁公开课 - 基础物理课程节选