Which of the Following Was an Important Discovery in the Field

Which of the following was an important discovery in the field of plant genetics?

A) Within plant species there is little variation in form because there is little genetic variation.
B) Complexity of structure corresponds to complexity of basic plant components.
C) In a given species, small genetic differences can lead to large differences in plant form.
D) In a given species, large genetic differences are necessary for large differences in form.
E) Large differences in the forms of different species are always caused by large genetic differences.