The rapid increase of population in the west resulted from the discovery of a. gold and silver deposits. c. the lush forests of the northwest. b. a major oil field in alaska. d. plentiful fish off the coast.

a.  gold and silver deposits.

Explanation:

As the increase of the population in western sides took place the discovery of the gold and that of the silver deposits were found in many parts of the world. and abundance of the natural wealth of resources. The gold rush in California is one of them and brought 300,000 people to the state form the rest of the united states and abroad.