Answer:
b. most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species
Explanation:
Species can evolve fast or slowly. When species accumulate changes at a slow rate this is called gradualism.
If a species suddenly has a an enormous change for example through mutations in the genes of a few individuals or a single individual the species can has evolve and may become suddenly a new one. A good example can be found in the following link: https://blog.education.nationalgeographic.org/2018/02/07/cloned-crayfish-are-taking-over-the-world/
the article provides evidence of sudden changes that may lead to speciation in at a really fast rate.
