In which of the following situations is evolution by natural selection most likely to occur?

a. A population of snails with unlimited resources and no predators
b. A population of mountain gorillas in which individuals with genes for long hair survive the cold better
c. A population of howler monkey in which all members produce the same number of offspring
d. A population of island birds that possesses no genetic variation

Natural Selection refers to the survivability of organisms based on different traits or genes that they have which then get passed on to their offspring. Based on this information we can say that a population of mountain gorillas in which individuals with genes for long hair survive the cold better is the situation in which natural selection is most likely to occur. This is because longer hair in this scenario is a gene that drastically affects the chance of survival for the gorillas and will most likely be passed on to their offspring.

I hope this answered your question. If you have any more questions feel free to ask away at Brainly.