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.

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.

they absorb it i think

not sure

you