Final answer:
The subject of this question is Physics. The correct answer is D) A challenging obstacle. When sprinting on a hill, the climb is difficult and requires effort and energy.
Step-by-step explanation:
The subject of this question is Physics. The question is asking about the transition that occurs during sprinting on a hill. The correct answer is D) A challenging obstacle. When sprinting on a hill, the climb is difficult and requires effort and energy. As the sprint continues, it becomes a challenging obstacle to overcome.