Option 1 -> Consumption that occurs even at zero income level, independent of income.
Option 2 -> Not a standard economic term; investment and consumption are separate concepts.
Option 3 -> Refers to planned or expected consumption, not minimum consumption at zero income.
Option 4 -> Refers to actual consumption after the fact, not minimum consumption at zero income.
Hence, Autonomous consumption -> In the consumption function C = a + bY, 'a' represents autonomous consumption - the basic minimum level of consumption required for survival (food, shelter, clothing) that occurs even when income is zero. It is financed through past savings, borrowing, or dissaving. This is independent of current income level and forms the intercept of the consumption function. -> correct