Ben bakes bread and Shawna knits sweaters. Ben and Shawna both like to eat bread and wear sweaters. In which of the following cases is it impossible for both Ben and Shawna to benefit from trade?

A、Ben cannot knit sweaters and Shawna cannot bake
bread.;
B、Ben is better than Shawna at baking bread and
Shawna is better than Ben at knitting sweaters.;
C、Ben is better than Shawna at baking bread and at
knitting sweaters.;
D、Both Ben and Shawna can benefit from trade in all
of the above cases.