Explanation:

To calculate economic growth, you need to estimate the total actual production of the last year and compare it to that of next year.

Option A: Market cost calculations include inflation, and thus a mere increase in prices will indicate an increase in GDP even if there has not been an actual production increase. So, A is wrong.

Option B: GNP at factor cost is more realistic because it also takes into account the NFIA as well as factor cost (which is the manufacturing cost). But, then it does not take into account the depreciation of goods in the economy which effectively reduces the total effective production of last year.

Option C and D: By these means, option D is the best choice, as option C is calculated at market cost.