____ difficult it is to surmount the obstacles, we're bound to achieve our goa.
A、As
B、How
C、So
D、However
【正确答案】：D
【题目解析】：【考点点击】本题考查让步状语从句。【要点透析as引导让步状语从句时,常将从句的补语或状语置于句首,如: Difficult as it isto.how意为“多么地”,引导感叹句或一般疑问句;so意为“因此,因而”; however意为“无论如何,不管怎样”,引导让步状语从句,相当于no matter how,符合题意
