In India, cluster bean (Guar) is traditionally used as a vegetable or animal feed, but recently the cultivation of this has assumed significance. Which one of the following statements is correct in this context?

Option B is correct. The gum (guar gum, a galactomannan polysaccharide from the seed endosperm) is a cheap, effective thickening agent. It is used in hydraulic fracturing fluids, which carry sand into shale rock formations to release gas. Demand jumped during the shale gas boom after 2010, and India, mainly Rajasthan, Haryana and Gujarat, became a major supplier.

Why the others fail:

• A: Guar seed oil is not the basis for biodegradable plastics. The commercial value of the crop lies in the gum, not the oil.
• C: There is no established antihistamine property of guar leaf extract that makes it a valid answer here. Antihistamines are a pharmacology topic, and this claim is not part of the standard syllabus fact.
• D: Guar seed oil content is low, and it is not a recognised high-quality biodiesel feedstock.

Mains angle: this is a good example of how a traditional legume (a nitrogen-fixing crop suited to arid Rajasthan) acquired industrial value and export income, which links to crop diversification, MSP debates and farmer income.

Trap: Aspirants either pick the "biodegradable" or "biodiesel" option because it sounds modern, or they remember guar only as fodder and forget its industrial gum use.