Solution:If the consumption function passes through the origin and the average propensity to consume (APC) is equal to the marginal propensity to consume (MPC), then the consumption function is linear :
Explanation - The slope of the consumption function is the MPC. If the MPC is constant, then the consumption function is linear and will be represented as a straight line.
Definition - The APC is the percentage of income spent on goods and services. The MPC is the ratio of the change in income.