which is not a reason of maximum diversity topics\thighest pest pressure\tevolutionery older zone\thigh rate out of crossing\tgreater environmental variations

Correct option is 4.
Biological diversity is the variety of species of living beings of an ecosystem. In ecosystems which are more biodiverse, like tropical forests, a great variety of plants, microorganisms and animals live; in ecosystems less biodiverse, like deserts, there are less variety of living beings.