Environmental factors can influence natural selection because they can increase or decrease
the number of chromosomes in an individual.
the number of chromosomes in a population.
the amount of genetic variation in an individual.
the amount of genetic variation in a population.

Answer is the amount of genetic variation in a population Natural selection gets impacted by environmental factors.

The environmental factors increase or decrease the quantum of genetic variation in a population. Genetic diversity increase due to sudden and permanent change in the gene or DNA. This change is called mutation. Decrease in genetic diversity may occur when a specific allele reduces the chances of individual with that trait to reproduce. Individual with decreased genetic variation often dies before producing offspring through reproduction.