几道语法题

问题描述：

几道语法题
1.I thought the technician was to blame for the blowing of the fuse,but I see now how I was mistaken.
2.For him to be re-elected ,what is essential is not that his policy works,but that the public believe that it is.
3.If they will not accept a check,we shall have to pay the cash,though it would be much trouble for both sides.
以上三题划横线的错误应如何改正
下划线被吞掉了，1是how，2是最后面那个is，3是the cash