For a Single-Price Monopolist,why Is Marginal Revenue Less Than Price

For a single-price monopolist,why is marginal revenue less than price?

A) Because the firm is a price taker.
B) To sell another unit, the price must be lowered.
C) Demand is elastic when another unit is sold.
D) Demand is inelastic when another unit is sold.
E) The question is false because marginal revenue is always equal to price.