Which major Indian river enters the sea through an estuary and does not form a large delta?

Correct answer: Narmada

A delta develops when a river loses speed near its mouth and deposits sediment in several distributary channels. An estuary is a broad, tidal river mouth where freshwater mixes with seawater; strong tidal action can remove or redistribute sediment and prevent the formation of a large delta. The Narmada flows westward through a rift valley and enters the Arabian Sea near the Gulf of Khambhat through an estuarine mouth. Therefore option B, Narmada, is correct. Godavari, Krishna, and Mahanadi flow generally eastward and are well known for forming large deltas on the Bay of Bengal coast. The answer depends on identifying the river-mouth landform and drainage direction, not simply on comparing river lengths. The contrast between estuary-forming Narmada and delta-forming east-flowing rivers makes the choice unambiguous.