问题
选择题
He tried his best to solve the problem, _______ difficult it was.
A．whatever
B．however
C．whichever
D．wherever
答案
答案：B
题目分析：No matter +特殊疑问词引导让步状语从句，意为：无论…；意为后面接形容词difficult，所以使用how.而不是what. 句意：无论问题有多难，他都全力以赴地解决它。故B正确。