For a pure monopolist the relationship between total revenue and marginal revenue is such that:

A) marginal revenue is positive when total revenue is at a maximum.
B) total revenue is positive when marginal revenue is increasing,but total revenue becomes negative when marginal revenue is decreasing.
C) marginal revenue is positive when total revenue is increasing,but marginal revenue becomes negative when total revenue is decreasing.
D) marginal revenue is positive so long as total revenue is positive.

For a pure monopolist, marginal revenue is initially positive when total revenue is increasing because the firm is able to sell additional units of output at a price higher than the cost of producing them. However, as the monopolist continues to increase output, the marginal revenue curve eventually slopes downwards because the additional revenue gained from selling an additional unit of output is outweighed by the decrease in price needed to sell that unit. Therefore, marginal revenue eventually becomes negative when total revenue is decreasing.