Final answer:
The correct answer is a) Newton's 1st Law. Newton's first law, also known as the law of inertia, states that an object will remain at rest or in motion at a constant velocity unless acted on by an external force.
Step-by-step explanation:
The tendency of a moving body to keep moving and a body at rest to stay at rest is described by Newton's first law of motion. This law, often referred to as the law of inertia, defines that a body at rest remains at rest, or, if in motion, remains in motion at a constant velocity unless acted on by a net external force. Therefore, the correct answer to the given question is option a) Newton's 1st Law.
In more detail, the law of inertia (Newton's First Law of Motion) implies that objects have a natural tendency to maintain their state of motion. The law explains that a body will only change its motion if it is subjected to an external force. Thisis related directly to the concept of inertia, which is dependent on the object's mass, indicating the quantity of matter within.