How many minutes must the target heart rate be maintanied in order for aerobic exercise to be beneficial

Which step in healthy decision making requires you to look at the decision you made and determined whether different actions would have produced different results

Ihave a really high metabolism and only weigh 70 pounds (13 almost 14). people always ask me two questions: do you ever eat and how do you eat so much and stay so skinny. i am worried that a high metabolism wont me forever. what are some safe steps i can take to maintain being fit. (also, i already work out i am a dancer so i get cardio a lot)

Whihc type of medicine kills cancer cells in the body, but also kills healthy cells