Water flow in a river depends on which of the following factor (s)?

size of its catchment area and rainfall within its catchment area

The correct answer is Option 2: size of its catchment area and rainfall within its catchment area

The amount of water flowing in a river mainly depends upon:

• the size of the catchment area, because a larger catchment collects more water, and
• the rainfall received within the catchment area, because rainfall directly supplies water to the river.

Option 3: no of tributaries and rainfall within its catchment area This is Incorrect because it omits the catchment area, which is the physical boundary that defines the supply region for the entire river network. While tributaries are part of the network, they do not function effectively without the geographic scale of a drainage basin to provide the necessary water input.

NCERT: Water flow in a river depends on size of its catchment area or river basin and rainfall within its catchment area.