Which resources most directly lead to the development of early civilisations in river valleys

Not only do the river valleys provide food resources such as fishing, they also often have a wide, fertile floodplain readily suited for agriculture.

Explanation:

Even the earliest, least advanced farming technology would have been successful in producing a substantial crop surplus from a river valley's naturally fertile soil. Agricultural innovations that had been developed elsewhere were introduced into the valleys of the river and developed on a larger scale. In Mesopotamia,  Nile Valley, the Indus Valley, vegetation, and livestock thrived in the great river valleys in a quite significant form, especially after irrigation technologies were established to maximize the use of the region around the river.

question - in 1827, john walker, a druggist in a small english town, tipped a splint with sulphur, chlorate of potash, and sulphid of antimony, and rubbed it on sandpaper, and it burst into flame. the druggist had discovered the first friction-chemical match, the kind we use to-day. it is called friction-chemical because it is made by mixing certain chemicals together and rubbing them. although walker's match did not require the bottle of acid, nevertheless it was not a good one. it could be lighted only by hard rubbing, and it sputtered and threw fire in all directions. in a few years, however, phosphorus was substituted on the tip for antimony, and the change worked wonders. the match could now be lighted with very little rubbing, and it was no longer necessary to have sandpaper upon which to rub it. it would ignite when rubbed on any dry surface, and there was no longer any sputtering. this was the phosphorus match, the match with which we are so familiar. according the paragraph what was the benefit of the new phosphorus match? it burst into flame when rubbed on sandpaper. it was made by mixing chemicals. it could be ignited on any dry surface. it threw fire in all directions.

answer - matches required natural chemicals

i believe your answer is mountains.