Victoria has her treadmill set to low for today's exercise routine. She can turn it up to high or turn it off. Which best describes what she did during the time shown on the graph? A-After 15 minutes, she turned it down to low for 30 minutes. She then turned it off. B-After 15 minutes, she turned it up to high for 30 minutes, then back down to low for 15 minutes. She then turned it off. C-After 15 minutes, she turned it down to low for 30 minutes, then back up to high for 15 minutes. She then turned it off. D-After 30 minutes, she turned it up to high for 30 minutes. She then turned it off.