Please choose the correct ending to complete the given sentence: Tennis serve with ball bouncing: The animated graphic morphs into a real and actual version of the graphic, appearing on a outdoor tennis court and flanked by two men. the two men standing next to the machinery

Ending1: place tennis balls into the machine, which in turn spits out the balls acting as an automated tennis ball server for a player who is standing on the other side of the tennis court with a tennis racket. Ending2: are introduced and they were referring to the equipment that the man is demonstrating. Ending3: and preparing to demonstrate an exercise called javelin throw. Ending4: are doing various than normal exercises in consecutive activities, interspersed with occasional action in an unsuccessful attempt to aid in improving tennis.

Answer format: ending1/ending2/ending3/ending4