Answer:
A) In this wild mustard, there is enough heritable variation to permit these different varieties
Step-by-step explanation:
The mentioned varieties were created by artificial selection for various traits in the wild mustard Brassica. This wild type plant was native to Europe and Asia and had a wild range of genetic variations to allow the development of different strains.
For example, the selection of strains that formed the overlapping leaves led to the development of cabbage. Repeated breeding allowed this trait to become prominent as it is in the modern cabbages. Likewise, the strains of the wild cabbage that had prominent storage stem gave rise to kohlrabi while the strains with enlarged axillary buds were selected for the development of brussels sprouts.