Answer:
The correct answer is III. can result in the formation of a new species within a few generations.
Explanation:
When a population from a species who live in the same habitat isolate reproductively and form new species then this process is known as sympatric speciation. This speciation mainly results from the generation of polyploidy condition.
In polyploidy condition the chromosome numbers in the individuals become double. This condition most commonly occurs in plants. Then these polyploid plants can not reproduce with other diploid plants but can fertilize itself so it create a reproductive isolation with other members and produce new species. So in sympatric speciation formation of new species occurs within a few generations.