The key ___the problem is to meet the demand___by customers
问题描述：
The key ___the problem is to meet the demand___by customers
A.to solving,making Bto solving,made C,to solving,making D,to solve,made
答
选B,key to sth--某件事的关键.后面要跟名词,solving the problem是动名词,符合要求.made是被动语态,句子里是顾客所作出的要求.