The fact that monopoly and monopsony exist in resource markets means that:

A) the marginal productivity theory of income distribution is valid.
B) resource prices do not always measure contributions to output.
C) the resulting income distribution is ethically correct.
D) income shares do not exhaust the total output.

Monopoly and monopsony can lead to distortions in resource prices, meaning that prices may not accurately reflect the true value or contribution of a resource to output. This can result in inequitable income distribution and a failure to exhaust total output. The marginal productivity theory of income distribution does not factor in the effects of market power on resource prices, making choice A incorrect. There is no ethical judgment implied in the existence of monopoly and monopsony, making choice C incorrect.