Answer
d Ron in washing, neither in mowing
This is because both of them can mow only 1 lawn in one hour's time, and Ron can wash 3 cars in an hour's time while David can only wash 2 in an hour's time, hence option 'd' is correct.
Work Step by Step
Since David can mow a lawn and only give up washing 2 cars, David has an absolute advantage in mowing since Ron would have to give up washing 3 cars. Since Ron can wash 3 cars and only give up mowing a lawn, Ron has an absolute advantage in washing since David could only wash 2 cars with giving up mowing a lawn.
