tiaojian zheme shao?

原题就是这样的吗？？？？？？？

它是一个独立的小题目，条件就那么多。

Do you mean weak exogenous Exu=0? If so
(1) OLS is fine as long as you use Newey-West serial correlation robust standard error.
(2) If there are other variables z satisfying Ef(z)u=0, then the efficient estimator is GMM. OLS is special case of GMM in the sense that f(z)=x.

真是太感谢了
谢谢谢谢谢谢！