What is usually true about the control of a characteristic that shows discontinuous variation?
It is controlled by one gene or a few genes and is not moved by the environment✓الإجابة الصحيحة
It is controlled by many genes working together, and the environment can shift individuals between categories
It is controlled entirely by the environment, with no genes involved
It is controlled by one gene, but diet can move an individual into another category
الشرح
A small number of genes with a small number of distinct combinations produces a small number of distinct results, which is why the categories stay separate and an individual stays in the one it was born into. Expecting the surroundings to move someone between categories would blur those boundaries and turn the characteristic into a measured range instead.