Final answer:
A strength-training activity is an exercise that helps build and strengthen muscles. Sit-ups are an example of a strength-training activity that targets the abdominal muscles and helps improve core strength.
Step-by-step explanation:
A strength-training activity is an exercise that helps build and strengthen muscles. One example of a strength-training activity is sit-ups. Sit-ups target the abdominal muscles and help improve core strength. Other examples of strength-training activities include weightlifting, push-ups, and squats.
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