The domestication of plants and subsequent breeding has given rise to many different familiar crops. The single species of Brassica oleracea has given us many different vegetables including: kale; cabbage; broccoli; cauliflower; kai-lan; brussels sprouts and kohlrabi. Even though these are all the same species, this is possible because of:.
A. Genetic modification.
B. Varietal selection and conventional breeding.
C. Organic farming practices.
D. DNA transfer technologies.
E. Genomics and DNA sequencing.

Option B is correct

Explanation:

The given situation is possible because of varietal selection and conventional breeding

Varietal selection is the selection of varieties on fields of finished or near-finished products from plant breeding programmesConventional breeding (classical breeding or traditional breeding), is the development of new varieties (cultivars) of plants by using older tools and natural processes, as opposed to the newer, more sophisticated and sometimes radical tools of molecular plant breedingThere is a great diversity from single species of Brassica oleracea which has given many different types of vegetables Conventional breeding achieves it by crossing together plants with relevant characteristics, and selecting the offspring with the desired combination of characteristics, as a result of particular combinations of genes inherited from the two parents and deliver genetic crop improvement

B.

Explanation:

As given here, the domestication of plants and subsequent breeding varieties has given rise to many different familiar crops. Through this, the single species of Brassica oleracea  give different vegetables like: kale, cabbage, broccoli, cauliflower, kai-lan, brussels sprouts and kohlrabi, this is possible because of Varietal selection and conventional breeding.

That statement is true.