Step 1: Understand the classification of sectors.
- Primary sector: Involves extraction of natural resources (agriculture, fishing, mining).
- Secondary sector: Involves processing and manufacturing of goods, including electricity and gas generation.
- Tertiary sector: Involves services such as transport, education, trade, etc.
Step 2: Map the activity.
Gas and electricity are not raw resources (primary) but outcomes of processing and conversion of resources like coal, water, or natural gas into energy. Hence, they fall under the Secondary sector.
Step 3: Eliminate wrong options.
(A) Primary sector: Wrong, because electricity production is not raw extraction.
(C) Tertiary sector: Wrong, it does not produce but provides services.
(D) None of these: Wrong, because one correct sector exists.
Step 4: Conclusion.
The correct answer is (B) Secondary sector.