Jamila has been walking for 20 minutes after dinner every night for a few months now. At first, she really noticed that she felt better, but now she is starting to feel like it is not doing much. What can she do to ramp up the intensity?

A. She can start focusing on diet as well as exercise.
B. She can ask a friend or family member to join her.
C. She can take a more challenging walk that includes hills.
D. She can become more committed to walking every night.