But most of the easy substitution has already been done.

但是绝大多数的简单替换已经被做过了。

youdao

But most of the easy substitution has already been done.

但容易实现的替代材料多数已经投入应用。

youdao

But most of the easy substitution has already been done.

但容易实现的替代材料多数已经投入应用。

youdao