What do barbell curls and dips have in common? A. They are both leg exercises. B. They both use free weights. C. Neither exercise is isotonic. D. They are both arm exercises.

The question is asking to choose among the following choices that the barbell curls and dips have in common, base on my research and further investigation, I would say that the answer would be letter D. They are both arm exercises. I hope you are satisfied with my answer

The answer is D. They are both arm exercises.