Hello! I'm a highschool teacher in physics. I will teach Newtons third law this coming week and found the following question (regarding a horse pulling a carriage): "If the force on the carriage is equal and opposite to the force on the horse how can the horse pull the carriage? Is the answer: (a) The horse cannot pull the carriage because the carriage pulls as hard on the horse as the horse pulls on the carriage. (b) The carriage moves because the horse pulls slightly harder on the carriage (c) The horse pulls the carriage before it has time to react. (d) The horse can pull the carriage only if the horse is heavier than the carriage. (e) Another explanation. What might it be?" For me, the correct answer is (e). I think of the force from the carriage as being the force due to the inertia of the carriage. I.e. when the horse match the force of the carriage, it implies the acceleration. How would you formulate the correct answer? Thanks!