When a student exerts a force on a lab cart that is carrying some masses, the acceleration is 3.0 m/s2. If the force is tripled and exerted on the cart with a total mass of one-half the original, then the acceleration will be O A. 1.5 m/s2 O B. 6.0 m/s2 O C. 18 m/s2 O D. 9..0 m/s2