I believe it to be D.
Some base sequences code for protein production. It codes for amino acids which then make the protein.
It's not that common actually quite rare because gray eyes are less than 1 percent of the earth population. Being that blue eyes and black hair is considered genetically impossible gray eyes are lighter, which makes it even more most likely impossible.
Fun fact: 10,000 years ago blue eyes didn't exist they are a mutation and everyone with blue eyes is technically related.
Answer: floods, forest fires, earthquakes
Explanation:
The short term changes are those changes that affects the organisms immediately. The effect of these changes remain for short duration. Thus the environment and the living beings adapt the changes. A flood can wipe out the terrestrial ecosystem, the ecosystem will regain its original form when the water level depletes. Forest fires may kill several trees and animals in an ecosystem. But some plants and animals will sustain which can give birth to new colonies. The earthquakes affect the earth crust and biosphere. The earth crust may get stabilize again by filling up the crater and biosphere will also promote of living beings.
I believe it would be A. because that is the muscle that regulates the heart pumping. This would happen because the pacemaker is taking over and it now has no purpose.