Which of the following statements is true about monopolies?

I- A monopoly is a market structure in which there is only one seller and many buyers.
II- A monopolist can raise its price above the competitive level by reducing the volume of production.
III- Many monopolies are aware that they can increase their profits by charging different prices to different consumers: they carry out price discrimination.
a) Only I is true.
b) Only II is true.
c) Only III is true.
d) II and III are true.
e) All statements are true.