Question 1:

What is the difference between a classic monopoly and a natural monopoly? What makes a classic monopoly a classic monopoly and what makes a natural monopoly a natural monopoly?

Question 2:

What causes a marginal revenue and demand curve to split in imperfect competition? I think. Or

What causes a marginal revenue and demand curve to split in half in imperfect competition?

For both questions, if you think it is worded wrong, please modify it so that it makes sense in the subject AP Microeconomics.