Cells are the basic unit of structure and function in organisms.
Needless to say, organisms can’t be a thing if cells didn’t exist.
The answer is D has mitochondria and chloroplasts. In the leaf, so must have chloroplast, most eukaryotic cells have mitochondria (powerhouse of the cell)

Actually Welcome to the Concept of the Genes.
Basically a Polygenetic trait is controlled by two or more genes.
Examples of human polygenic inheritance are height, skin color, eye color and weight. Polygenes exist in other organisms, as well.