For a Monopolist with a Downward-Sloping Demand Curve

For a monopolist with a downward-sloping demand curve,

A) the coefficient of price elasticity of demand is infinite.
B) the coefficient of price elasticity of demand is zero.
C) as price increases, marginal revenue decreases.
D) as price decreases, marginal revenue decreases.
E) when the price is equal to zero, marginal revenue is equal to zero.