Which of the following is NOT correct ?

Peninsular India's rivers are conventionally split into an east-flowing group, which drains into the Bay of Bengal, and a west-flowing or independent group, which drains into the Arabian Sea or into inland basins. Within each group, every river has well-documented facts about its source, course, and comparative rank by length and drainage-basin area, and these facts are tested directly in this kind of question.

Checking each statement against this classification: the statement about Krishna's rank among the east-flowing Peninsular rivers matches the standard ranking; the statement about Kaveri's source matches its documented origin in the Brahmagiri Hills; and the statement about Luni matches its status as the principal river system of western Rajasthan. The statement about the Peninsula's largest river system, however, reverses the established ranking: the river named there actually occupies the top spot by both length and drainage-basin area, so the claim that it is not the largest is factually incorrect.

• Krishna: ranks second among the east-flowing Peninsular rivers by length and basin area — this statement is accurate.

• Kaveri: rises in the Brahmagiri Hills of the Kodagu district, Karnataka — this statement is accurate.

• Godavari: is actually the largest Peninsular river system by both length and drainage-basin area, often called the 'Dakshin Ganga' — so the claim that it is NOT the largest misstates the ranking.

• Luni: is the principal, largest river system of western Rajasthan, an inland-draining (endorheic) river that ends in the salt marshes of the Rann of Kutch — this statement is accurate.

Since the statement about the Peninsula's largest river system is the only one that misstates a ranking fact, it is the statement that is NOT correct — the answer to this question.