You will be given a definition of a task first, then some input of the task.
In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

[header] How to stay fit in middle school [title] Get moving. [step] Doctors advise that middle schoolers get at least an hour of physical activity every day: that's 60 minutes of moderate aerobic activity like walking or intense activity like running. Regular exercise will give you stronger bones and better skin, help you keep a stable weight, and give you mental and mood boosts. <sep> (A) [substeps] Using low-impact exercise throughout the day can keep your body healthy and help you stay fit. Cross physical activity out of your schedule and towards your goals. (B) [substeps] Do things you enjoy! Exercise doesn't have to be a chore. Do you like to rollerblade, play basketball, dance, or ride your bike? These are all great-and fun-physical activities. (C) [substeps] Aim for 150 minutes of exercise every week, or 150 minutes of vigorous exercise every week. Try to walk rather than jogging, and choose " low-impact " activities like tennis, cycling, and biking. (D) [substeps] Encourage your gym friends to join you in your morning classes. This will give them something to see outside of the classroom.
Output:
B