The maturity of a river course is recognized by the presence of

Answer: (b) Meanders

Meanders form in the mature stage on flatter ground.

The idea

In the classic river-stage model, a mature river spends more effort widening its valley than cutting it deeper. Bends grow as the current erodes one bank and deposits on the other. Use the overall valley and flow pattern rather than treating every bend as an exact age marker.

Channel develops bends → Faster outer-bank flow erodes → Slower inner-bank flow deposits sand → Bends enlarge and migrate → Floodplain widens → A bend may be cut off as an oxbow lake

Why the others are wrong

(a) V-shaped valleys mark the youthful stage.

(c) Gorges are youthful.

(d) High erosive power is youthful.

Elimination technique

V-shaped valleys, gorges and strong downward cutting belong to the youthful end of the classic model. The feature associated with lateral erosion and a widening valley is the meander.

Also know

A gorge and a V-shaped valley mainly indicate strong vertical cutting. An incised meander is a bend cut deeply into rock after uplift or a fall in base level, so meanders can occur in steep terrain too. Natural levees build beside channels during floods; an alluvial fan forms where a stream emerges onto gentler ground.