A retail margin is the difference between $\_\_\_\_\_\_\_\_$ and $\_\_\_\_\_\_\_\_.$

Question $1$Select one:

A$.$

the volume of merchandise ordered; the volume of merchandise sold

B$.$

the revenue generated by a retailer in a year; the taxes paid by a retailer in that same year

C$.$

the retailer's operating expenses; the retailer's revenue

D$.$

a product's retail selling price; a product's wholesale cost

E$.$

a product's wholesale cost; a product's mark$-$up