Final answer:
The gravitational force that a woman exerts on Earth while standing on it is equal to her weight, according to Newton's Third Law of Motion.
Step-by-step explanation:
When a woman stands on the Earth, the gravitational force she exerts on Earth is indeed equal to her weight. According to Newton's Third Law of Motion, every action has an equal and opposite reaction. Hence, if the Earth exerts a gravitational force on the woman, making her have weight, she exerts an equal force on the Earth, although we don't feel this due to Earth's much larger mass. The correct answer to the student's question is 'b) Equal to her weight'.