Which one of the following is a bio-diesel crop?

Concept: A bio-diesel crop is a plant cultivated primarily for its non-edible seed oil, which is converted through trans-esterification into biodiesel -- a renewable substitute for petroleum diesel. India's biofuel programmes single out such dedicated energy crops, as distinct from crops cultivated for a different primary purpose -- fibre, food, or sugar/ethanol -- where any usable seed oil, if present, is at most a secondary by-product.

Application: Among the four crops listed, Jatropha (Jatropha curcas) is the one cultivated in India specifically as a dedicated non-edible oilseed energy crop -- its seeds carry 30-40% oil content that is processed via trans-esterification into biodiesel, and Jatropha was the flagship crop of India's National Mission on Bio-Diesel (launched 2003), chosen for its ability to grow on marginal wasteland with minimal input.

• Cotton is grown primarily as a fibre crop for the textile industry; its cottonseed oil is only a secondary by-product used for cooking and industrial purposes, not a dedicated biodiesel feedstock.

• Sugarcane is grown for sugar and ethanol, produced by fermenting its juice or molasses -- a different biofuel pathway (fermentation) from biodiesel (trans-esterification).

• Potato is a starchy food crop grown for consumption; unlike the oil-rich Jatropha, it is not cultivated as a dedicated oilseed feedstock for biodiesel.

Cross-check: The distinguishing test is primary cultivation purpose -- cotton is grown for fibre (its cottonseed oil is only a secondary by-product), sugarcane for sugar and ethanol, and potato for food; none of these is cultivated as a dedicated oilseed energy crop. Jatropha alone is cultivated as a dedicated non-edible oilseed crop specifically for biodiesel, confirming it as the bio-diesel crop among the four.