因为我们没有以太的力学结构，所以很难答复这个问题。

Since we have no mechanical picture of the ether, it is extremely difficult to answer this question.

youdao

就上述事情，我方很难给予你方肯定的答复。

We are sorry not able to give you a definite reply in respect of the above matter.

youdao

有时我发现很难给一个肯定的答复。

Sometimes I found it very hard to give a certain reply.

youdao