_____ it is not his responsibili

_____ it is not his responsibility to do that, he said he would help.
A、Although
B、As
C、Since
D、Unless
【正确答案】：A
【题目解析】：although虽然；as因为；since自从；unless除非句意：虽然这不是他的责任，但是他说他会帮忙的。