The given question is related to the concept of "Force and Laws of Motion" from Class 9 Physics.

Answer Explanation:

According to Newton's third law of motion, "For every action, there is an equal and opposite reaction".

Let us analyze the given options one by one:

a) When the girl jumps from a boat to the shore, she exerts a force on the shore. As per Newton's third law, the shore would also exert an equal and opposite force on the girl. This force would act in the opposite direction to the girl's jump.

b) When a goalkeeper saves a goal, he applies a force on the ball. As per Newton's third law, the ball would also apply an equal and opposite force on the goalkeeper. This force would act in the opposite direction to the goalkeeper's hand.

d) When a person pushes a wall, he exerts a force on the wall. As per Newton's third law, the wall would also apply an equal and opposite force on the person. This force would act in the opposite direction to the person's push.

c) When a horse pulls a cart, it applies a force on the cart. As per Newton's third law, the cart would also apply an equal and opposite force on the horse. This force would act in the opposite direction to the horse's pull.

Hence, option 'C' is the correct answer.

Key Points:

- Newton's third law states that every action has an equal and opposite reaction.
- The force always acts in pairs, and the two forces are equal in magnitude but opposite in direction.
- Understanding this law helps us explain many everyday actions such as walking, jumping, pushing, and pulling.