Which law is also known as the law of inertia?

Newton's First law of motion

The correct answer is option 2. Newton's First law of motion.

The law also known as the law of inertia is Newton's First law of motion. Newton's First law of motion is often referred to as the law of inertia. It states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This law describes the tendency of objects to resist changes in their motion, which is commonly referred to as inertia.