问题
选择题
He tried his best to solve the problem, difficult it was.
A．no matter what
B．whatever
C．however
D．how
答案
C
题目分析：考查状语从句。句意：他努力去解决这个问题，无论它有多么的困难。后半句是让步状语从句，however相当于no matter how 后面跟形容词或副词,而whatever 等于no matter what后面跟名词，故选C项。
考点 : 考查状语从句