It takes Mom 30 minutes to cook dinner. In the same time, she can iron 6 shirts. Dad takes an hour to cook dinner and 30 minutes to iron a single shirt. A) Dad has an absolute advantage in ironing shirts. B) Mom's opportunity cost of cooking dinner is ironing 6 shirts. C) Mom has a comparative advantage in cooking dinner. D) Dad's opportunity cost of cooking dinner is ironing half a shirt. E) Dad's opportunity cost of cooking dinner is 6 shirts.

Why is he answer not C as well?