It is difficult to start motion with a heavy box and also difficult to stop it once it's moving. This best exemplifies:

Correct — C. Inertia is a body's resistance to any change in its state of rest or uniform motion.

The stem shows both halves: the box resists starting (inertia of rest) and resists stopping (inertia of motion).

A heavier box shows more of it. By Newton's second law, the same force gives a larger mass a smaller acceleration, whether that force is speeding the box up or slowing it down. That is option (c).

Why the others are wrong

• (a)
  The concept of power — Power is the rate of doing work, measured in watts. It tells how fast energy is transferred, not why a body resists being started or stopped.
• (b)
  Conservation of energy — Conservation of energy says total energy stays constant while it changes form. It sets no resistance to starting or stopping a box, which is what the stem describes.
• (d)
  Action-reaction principle — The action-reaction principle is Newton's third law: forces come in equal and opposite pairs acting on two different bodies. The stem describes one box resisting change, which is the first law.

Newton's first law is the law of inertia: a body at rest stays at rest, and a moving body keeps a constant velocity, unless a net force acts on it.

NCERT's Class XI Physics puts it in three words: inertia means resistance to change.

The second law adds the amount. Acceleration is inversely proportional to mass, so a heavier body resists a change in motion more strongly. This is why mass is called the measure of inertia.

Key facts

• Newton's first law: a body at rest stays at rest, and a moving body keeps constant velocity, unless a net force acts on it.
• Inertia means resistance to change in a body's state of rest or uniform motion (NCERT Class XI Physics, Chapter 4).
• Newton's second law: for the same net force, a larger mass has a smaller acceleration.
• Newton's third law: to every action there is an equal and opposite reaction, acting on a different body.

Common traps

• Choosing action-reaction because a push is involved, when the third law is about force pairs between two bodies, not one box resisting change.
• Reading 'difficult' as a matter of energy or power, when the stem describes resistance to a change in motion.

No directly related past PYQ was found.