Can you please give the correct answer for this question and explain your reasoning?

If total costs remain the same, the smaller the proportion of fixed costs in a firm's cost structure:

A.the greater the impact on profit from a percentage change in sales volume.

B.the smaller the impact a percentage change in sales volume will have on profit.

C.the lower the contribution margin.

D.the smaller the impact a percentage change in sales volume will have on profit AND the lower the contribution margin.