Engel's law states that as the income of a household rises

The correct answer is C, marginal productivity of labour is zero. Disguised unemployment, also called hidden unemployment, exists where more persons are engaged in a job than are actually needed, so withdrawing one of them would not reduce output at all; that worker's marginal contribution is therefore zero. Indian agriculture is the classic illustration, where a whole family works on a holding that two members could manage. Option A is wrong because open unemployment, where people are visibly without work, is a different category altogether. Option B is wrong because the absence of alternative employment is a cause of the condition, not its definition. Option D is wrong because low productivity may arise from poor tools, poor soil or poor skills, which is a matter of degree, whereas disguised unemployment refers specifically to the zero marginal product of the surplus worker.

The correct answer is B, structural unemployment. It arises when the structure of the economy changes, so that the jobs being created need skills different from those the available workers possess; it lasts long and is cured by retraining and education rather than by a revival of demand. Option A, seasonal unemployment, is wrong because that is the idleness of workers in the months when their occupation offers no work, as in agriculture between sowing and harvest or in the sugar and ice industries. Option C, economical, is wrong because there is no recognised category of that name in economics. Option D, frictional unemployment, is wrong because it is the short-lived joblessness of people moving between one job and the next, which exists even in a healthy economy and is sometimes called search unemployment.

The correct answer is C. The repo rate is the rate at which the Reserve Bank of India lends short-term money to commercial banks against the collateral of government securities under a repurchase agreement, which is where the name repo comes from; it is the policy rate announced by the Monetary Policy Committee and the signal for interest rates across the economy. Option A is wrong because the rate a bank charges its own customers is its lending rate, now linked to external benchmarks. Option B is wrong because the government does not lend to banks; borrowing and lending to banks is central banking work. Option D is wrong because it describes the reverse repo rate, under which banks park their surplus funds with the Reserve Bank, and raising that rate absorbs liquidity from the system.

The correct answer is B, 15 and 59. Indian statistical practice treats persons aged fifteen to fifty-nine years as the working age population, and the labour force is made up of those among them who are either working or seeking and available for work. Children below fifteen are expected to be in school, and persons of sixty and above are counted as elderly dependants, so both groups are left out of the workforce. Option A is wrong because a range from ten to sixty-nine would count child workers and the elderly. Option C is wrong because fifty-five is a retirement age in some services but not the statistical boundary. Option D is wrong because eighteen is the age of majority and voting and sixty-five a retirement age, not the limits used for the workforce in Indian data.

The correct answer is A. Gross domestic product counts what is produced inside the domestic territory, whoever produces it, while gross national product counts what is produced by the normal residents of the country, wherever they are; the bridge between them is net factor income from abroad, which is the income Indians earn abroad minus the income foreigners earn in India. Option B is wrong because subtracting depreciation from gross domestic product gives net domestic product. Option C is wrong because the relation between factor cost and market price turns on indirect taxes minus subsidies, which is a different adjustment. Option D is wrong because dividing by the population gives per capita product or income, which measures the average rather than the total, and is the figure used to compare living standards between countries.