Option 1 -> Incorrect sequence; cannot add NFIA before calculating domestic income.
Option 2 -> Incorrect sequence; classification must precede estimation.
Option 3 -> Incorrect sequence; identification should come first, not estimation.
Option 4 -> Correct logical flow: identify units first, then estimate their income, calculate domestic total, finally add NFIA.
Hence, Option 4: (C), (B), (D), (A) -> The income method follows a systematic approach: First, (C) Identify and classify income-generating units (primary, secondary, tertiary sectors). Second, (B) Estimate factor income earned by each sector (wages, rent, interest, profits). Third, (D) Calculate domestic factor income by summing all sectoral incomes. Finally, (A) Add Net Factor Income from Abroad to arrive at National Income (NDPFC + NFIA = National Income). This sequence ensures accurate measurement from micro to macro level. -> correct