Final answer:
The correct statement explaining why Newton's first law is valid even when objects stop is that most objects are affected by unbalanced forces such as friction, which causes them to slow down and stop. So the correct option is C.
Step-by-step explanation:
The correct statement that best explains why Newton's first law is correct, even though real-world objects tend to eventually stop moving instead of remaining in motion, is:
C.) Most objects are affected by unbalanced forces such as friction.
Newton's first law of motion, also known as the law of inertia, states that a body at rest tends to remain at rest, and a body in motion tends to remain in motion with a constant velocity unless acted upon by a net external force. Applying this principle to an object sliding across a surface, it slows down and stops because of the net force of friction, not because the law does not hold. In a hypothetical scenario where friction and other external forces like air resistance are nonexistent, an object in motion would continue to move indefinitely at a constant velocity, as Newton's first law describes.