Question

which of these best explains the difference between prezygotic barriers and postzygotic barriers?
prezygotic barriers keep zygotes from forming while postzygotic barriers involve formed zygotes.
postzygotic barriers always cancel out prezygotic barriers but both allow formation of zygotes.
prezygotic barriers are barriers that help postzygotic barriers easily form multiple zygotes.

Explanation:

Prezygotic barriers act before fertilization to prevent zygote formation. Postzygotic barriers act after fertilization on already - formed zygotes.

Answer:

Prezygotic barriers keep zygotes from forming while postzygotic barriers involve formed zygotes.