Answer: B) The opposing force of friction stopped the train.
Explanation:
From Newton's first law of motion, we know that an object remains in the state of rest or constant motion unless and until acted upon by an unbalanced net force.
Here, the rolls to a stop along a horizontal track without application of break. There is absence of an applied force. It means that a force of friction acting in the opposite direction of motion train eventually brought it to rest state. Hence, the correct option is B.
