____ scientists have done a lot of researth on the (H1H1) flu,there are some class for further.
问题描述：
____ scientists have done a lot of researth on the (H1H1) flu,there are some class for further.
A.As B.Once C.If D.Although
答
选D.although 尽管.这是让步状语从句.
尽管科学家们在研究H1N1上做了很多,但是任重道远.