Concept:The accelerator principle connects investment to changes in income.Explanation:The accelerator principle states that investment is a function of the rate of change of income.This means when income rises or falls, investment changes by a larger proportional amount.In simple terms, I=f(ΔY), where I is investment and ΔY is the change in income.Therefore, among the given options, option C correctly expresses this principle.Answer:Investment is a function of the rate of change of income.