According to the punctuated equilibria model,
a. given enough time, most existing species will branch gradually into new species.
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.
c. most evolution occurs in sympatric populations.
d. speciation is usually due to a single mutation.

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.

the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

i hope this : )