All else equal, the contribution margin must increase as: A. Both Sales price and variable cost per unit increase. B. The fixed cost per unit declines C. The variable cost per unit declines D. Sales...

All else equal, the contribution margin must increase as:

A. Both Sales price and variable cost per unit increase.

B. The fixed cost per unit declines

C. The variable cost per unit declines

D. Sales price unit declines

E. The sales price minus the fixed cost per unit increases.

Which one of the following are correct. I think that the answer is A but not certain.