I often help mum ________ the housework because I think it’s good for me.

A. with B. in C. on D. of

A

句意：我经常帮助妈妈做家务，因为我认为这对我有好处。考查介词辨析题。help sb. with sth.帮助某人做某事，固定短语。根据句意语境，可知选A。