Which of the following is not an activity of the tertiary sector?

The correct answer is A, the primary sector. Mining takes a product straight out of nature without changing its form, exactly as farming, fishing and forestry do, and every activity of that kind is placed in the primary sector.

Option B, the secondary sector, would be correct only after the ore is processed: turning iron ore into steel is manufacturing and therefore secondary. Option C, the tertiary sector, covers services such as transport, trade and banking, which produce no goods of their own. Option D, the quaternary sector, is a modern extension used for knowledge based services such as research and software, and it does not appear in the standard threefold classification that examinations use. Candidates most often place mining wrongly in the secondary sector because it is heavy industrial work, so remember the test: if the product is taken directly from nature, it is primary.

The correct answer is C, the tertiary sector. It produces no goods at all; it provides services such as transport, storage, communication, trade, banking, insurance, education, health care and administration, which is why it is commonly called the service sector.

Option A, the primary sector, is also called the agriculture and allied sector, and option B, the secondary sector, is also called the industrial sector, so all three have a second name and papers exploit the confusion. Option D, the public sector, belongs to an entirely different classification, the one based on ownership rather than on the nature of the activity; a public sector enterprise may be in any of the three sectors, as a government owned coal mine, steel plant or bank shows. Keeping the three classifications apart is the main skill this chapter tests.

The correct answer is A, agriculture. On a small family holding every member of the household may work on the land even though the work needs far fewer hands; if some of them were withdrawn, total output would not fall. Their labour is therefore adding nothing, which is what disguised or hidden unemployment means.

Option B, information technology, and option C, banking, are organised service activities where posts are sanctioned and surplus workers are not carried in this way. Option D, mining, is organised and capital intensive for the most part. The other forms of unemployment are worth learning alongside: seasonal unemployment, where work exists only in certain months, which also afflicts agriculture, and open unemployment, where a person willing to work at the going wage finds none at all. Papers ask all three definitions in rotation.

The correct answer is B, 100 days. The Mahatma Gandhi National Rural Employment Guarantee Act, passed in 2005, guarantees one hundred days of wage employment in a financial year to every rural household whose adult members volunteer to do unskilled manual work.

Options A, C and D are plausible round numbers with no basis in the Act. Two further details are asked as often as the number itself. First, the unit of the guarantee is the household, not the individual, so the hundred days are shared among the adults of one family. Second, if work is not provided within fifteen days of the demand, an unemployment allowance becomes payable by the state government. It is these enforceable claims that make the law a rights based measure rather than a welfare programme that the government may or may not run.

The correct answer is A, the primary sector. Agriculture and its allied activities still give work to the largest number of Indians, even though the sector's contribution to national income is far smaller than that share of employment would suggest.

Option C, the tertiary sector, is the strong distractor, because services do contribute the largest share of national income; but income share and employment share are two different questions, and papers set them side by side precisely to catch the candidate who has learned only one line. Option B, the secondary sector, absorbed a large part of the workforce in the countries that industrialised early, which India has not repeated on the same scale. Option D, the quaternary sector, is a later refinement covering knowledge services. The mismatch between output and employment is the reason productivity and incomes per worker in agriculture remain low.