这是一个极其困难的问题。

This is an extremely difficult question.

youdao

然而，场论中的强耦合问题是极其困难的。

However, in the strongly coupled field theory problem is extremely difficult.

youdao

然而，场论中的强耦合问题是极其困难的。

However, in the strongly coupled field theory problem is extremely difficult.

youdao