Final answer:
The correct comparative phrase to describe the cheetah's speed relative to other animals is 'Much faster than', which is option A. This emphasizes the cheetah's superior speed without suggesting equality or inferiority.
Step-by-step explanation:
The correct answer to the question is option A, 'Much faster than'. When comparing the speed of the cheetah to any other animal, we use the comparative form 'much faster than' to indicate that the cheetah's speed is superior. Options B and C are grammatically incorrect, and option D, 'As fast as', would falsely suggest that the cheetah's speed is equal to that of another animal, which contradicts the intent of the statement as the cheetah is acknowledged as the fastest animal on earth.