(c) Nature of production activities
The classification into Primary, Secondary, and Tertiary sectors is based on the nature of production activities — primary involves natural resource extraction, secondary involves manufacturing, and tertiary involves services.
The examiner expects you to recall the basis of classification for each sector type. Primary/Secondary/Tertiary = type/nature of production activity. Organized/Unorganized = nature of employment (job security, terms of work). Don't confuse the two criteria. This is a direct factual recall question from Economics Chapter 2 (Sectors of the Indian Economy), though the passage here is from Chapter 1. The answer is standard textbook knowledge.