Answer:
The speed of the catapult arm needs to be increased.
Step-by-step explanation:
If the height needs to stay the same, they can not change the length of the catapult arm because this is the variable that determines the height of the thrown object. To change the horizontal distance the object travels, in other words the object's speed, the rope or counterweigth that pulls the catapult arm can be changed to increase the speed that the object is thrown.
I hope this answer helps.