its either a or b… but i could use some confirmation on that too!

it’s B – allopatric speciation occurs due to geograhpical isolation (barriers) like
the speciation of tilapia fish in lake turkana in kenya due to the lake drying up and separating the original group into three.

A is speciation between two groups in the same environment due to behavioural habits (one nocturnal and one diurnal), non-matching position of genetalia for reproduction (like a chihhuahua with a great dane) or formation of sterile hybrids (mule from a donkey and a horse)

i don’t know about E. D might deal with mutations. but C is the process by which one species evolves into different varieties to take advantage of other available niches in it’s habitat (or something like that)
for example, darwin’s finches in the galapagos islands.