Two species are able to breed with each other and produce offspring, but the offspring quickly die. this is a isolating mechanism. select one:
a. prezygotic
b. biochemical
c. sympatric
d. postzygotic
e. monophyletic

d. Postzygotic

Explanation:

The reproductive isolation is a mechanisms which includes geographical, physical and behavioral barriers which prevent members of two distinct species to mate and produce offsprings.

The postzygotic mechanism is an reproductive isolation mechanism in which the offspring/hybrid produce after the copulation of members of the two distinct species can be inviable or sterile.

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a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.