Answer:
The Lungs. The lungs play a mandatory role in the excretory system. Your lungs remove the carbon dioxide built up in your blood using specialized cells known as alveoli. Your lungs process the molecules into gas and when you breathe, the gas is ejected from your body.
Explanation:
C, because alleles are alternative forms of a gene that arise from mutation.
This question is not clear, but I think I understand what you are asking. The difference between alleles of a gene is that some alleles may be dominant or recessive. If one gene has more dominant alleles than another, than it will be more visible.
Ice age. It caused saber tooth and mammoth to die