Assume That the Consumer Is Correctly Applying the Rational Spending

Assume that the consumer is correctly applying the rational spending rule for normal goods X and Z.If the consumer's income increases,purchases of both X and Z rise because

A) the marginal utility of X decreases.
B) the price of Z falls.
C) the marginal utility of Z decreases.
D) combinations of X and Z that could not be considered before are now available.
E) the price of X increases.