Step 1: Understanding the Concept:
Newton's First Law of Motion, often called the Law of Inertia, describes the behavior of objects when the net external force acting on them is zero.
Step 2: Detailed Explanation:
The law states that an object will not change its motion unless a force acts on it.
• If the object is at rest, it stays at rest.
• If the object is in motion, it stays in motion with the same speed and in the same direction.
This resistance to change in the state of motion is known as inertia. Option (B) describes the second law, and option (C) describes the third law.
Step 3: Final Answer:
The statement in option (A) correctly defines Newton's first law of motion.