Crunches target the abdominal muscles. Although they can have benefits to arm and back strength depending on the variation chosen, most crunches will activate and load the abs. So the best answer is A.
Crunches are principally an abdominal exercise. Correct answer: A Crunches are exercises which target the rectus abdominis (or the '6-pack muscles' that run along the front of the torso). Crunches are a very good exercise for strengthening the core. The crunches are done by contracting the abs to bring your shoulders towards your hips.
