What is the primary concern with using dull clippers?

Using dull clippers primarily raises concerns about their ability to effectively cut hair. When clippers are not sharp, they can pull on the hair instead of making a clean cut, which can lead to discomfort for the client. This pulling action can cause pain and even injury to the scalp or skin during the haircut, resulting in an unpleasant experience.

While dull clippers can indeed be less efficient and might result in uneven hair lengths if not used properly, the immediate and most pressing concern is the discomfort they cause during use. B is correct in highlighting that the pulling and tugging of hair can lead to injury, making it essential for barbers to maintain their tools in peak condition for both the client's comfort and safety.