Explanation:

- Option 1: Consumption changes at a constant rate as income changes.

- This describes the simplest consumption function, where the marginal propensity to consume is constant.

- Option 2: Consumption changes faster with more income.

- This suggests that as income increases, consumption increases at an increasing rate, which is not assumed in the simplest consumption function.

- Option 3: Consumption does not change with income.

- This would mean consumption is always fixed, regardless of income, which doesn't align with the simplest consumption function.

- Option 4: Consumption changes with more supply.

- This suggests a relationship with supply, not income, which isn't part of the simplest consumption function.

Option 1: Consumption changes at a constant rate as income changes represents the simplest form of the consumption function.