Economic activities are grouped into sectors. The primary sector uses natural resources directly (agriculture, fishing, mining); the secondary sector transforms raw materials into finished goods; the tertiary sector provides services; and the quaternary sector covers knowledge-based activities such as research and information technology.

Manufacturing converts raw materials into more valuable products, for example cotton into cloth or iron ore into steel. Since it involves processing and production in factories, it belongs to the secondary sector of occupation.

The tertiary sector covers services such as transport, trade, banking and teaching, which do not produce goods. The sector that only extracts natural resources does not process them. The quaternary sector deals with knowledge and information services such as research and consultancy, not with making physical goods.

Secondary option is correct.