Which one of the following statements with regard to Newton’s third law of motion is not correct?

The correct answer is Option C.

Newton's Third Law describes a mutual interaction where forces occur in pairs. A key conceptual point is that action and reaction forces act simultaneously. There is no time delay between them, and thus no 'cause and effect' relationship where one precedes the other.

• Option A is a true statement: Forces never exist in isolation.
• Option B is a true statement: The stone and Earth exert equal and opposite forces on each other.
• Option D is a true statement: It correctly denies the cause-effect link.

Option C is the incorrect statement (and thus the answer) because it falsely claims a cause-effect relationship exists.