In a population of plants with a diploid number of 12, a new individual appeared with a chromosome number of 24. if this organism could self-fertilize, forming offspring with the same number of chromosomes (24), scientists would consider this an example ) sympatric speciation.

b) behavioral isolation.

c) formation of a hybrid zone.

d) reduced hybrid fertility.

A) sympatric speciation

Explanation:

Sympatric speciation leads to formation of new species from the existing one without the change in their location i.e. they share the same habitat but still become reproductively isolated from each other. It usually occurs in plants when they exhibit polyploidy.

Here, the plant species had originally 12 chromosomes and amongst them a plant appeared with tetraploid 24 chromosomes. Since plants can usually self fertilise, this plant can produce more offspring with 24 chromosomes without requiring a partner. The new plants with 24 chromosomes will form a different species from the original plant with 12 chromosomes.

the species living around the vents are especially good at dispersal.  

deep-sea vent originates on the floor of the ocean when seawater circulates through hot volcanic rocks, usually situated where the new oceanic crust is being produced.  

biological dispersal refers to the movement of species from their location of birth to their site of breeding, or from breeding site to another. similarly, the oceanic dispersal refers to the movement of the species from one land mass to another by sea crossing.