Suppose that the price of doughnuts decreases and that doughnut-holes are a by-product of producing doughnuts. One would expect:

A.the supply of doughnut-holes to increase.

B.the supply of doughnuts to decrease.

C.the quantity supplied of doughnuts to decrease.

D.the quantity supplied of doughnut-holes to increase.

正确答案：the quantity supplied of doughnuts to decrease.