For this question, look at the hydrologic cycle diagram.

which number represents runoff on this diagram?

a) 1
b) 2
c) 3
d) 4

The correct answer is D) 4.

Runoff is one of the event that occurs during water cycle. During runoff water flows over land as surface instead of being absorbed into the ground. Runoff may be the part of rain, melting of snow or water by irrigation water and amount of runoff depends on vegetation, use of land and amount of nutrients in the soil.

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.