Answer:
There is a difference in the external horizontal forces acting on the ball and the cart.
Step-by-step explanation:
When ball is thrown upwards from a moving cart then in that case the acceleration of the ball in vertical direction is due to gravity so it will raised up and again come back to ground.
While during this vertical motion it will also move horizontally with initial speed of cart at which it was moving at the moment when ball is thrown.
Now if ball is not landed on the cart again then we can say that both cart and ball are not accelerated with same acceleration in horizontal direction due to which they both will cover different distances in horizontal direction for the same time interval
So we can say that correct answer will be
There is a difference in the external horizontal forces acting on the ball and the cart.