The correct option is D Epidermis is too thin
While doing the onion peeling experiment, the major problem that everyone faced is to handle the onion epidermis as it is very thin and it folds in itself. The use of needles can be ineffective, or cause a disaster in the thin membrane. Thus, the thin epidermis is the most common problem that could be faced in the onion peeling experiment. Therefore, the correct answer is option A.