Please choose the correct ending to complete the given sentence: Tumbling: A girl is doing back flips on a blue mat. a girl

Ending1: in backflip is doing back flip in gym. Ending2: is standing on the mat on her hands and knees and working out. Ending3: does the splits in the air. Ending4: does backflips from the side of the mat on a blue mat.

Answer format: ending1/ending2/ending3/ending4