Answer:
The answer is A.
Explanation:
The example given in the question is based on two plants that are from the same family but they can not reproduce even though they should be able to because they belong to the same family.
This situation is an example of the option given in A, Sympatric Species, which can be explained as two species that share the same habitats and live in the same geographical location evolves in different directions and after a point can not produce offspring from interbreeding and therefore should be considered as different species.
I hope this answer helps.