Radioactive decay of 40k in an igneous rock has resulted in a ratio of 25 percent 40k atoms to 75 percent of 40ar and 40ca atoms. how many years old is this rock?

The biome pictured above is found in areas such as kenya and south africa. the land is grass-covered with very few trees and gazelles and other grazers are common here. why does this biome have a low population of trees? a) large grazing animals destroy the trees. b) it is a deforested rainforest with poor soil. c) it has high temperatures and low precipitation. d) it has a long rainy season followed by flooding.