The correct option is
A Stratum corneum
The stratum corneum is the outermost layer of the epidermis, consisting of dead cells. The purpose of the stratum corneum is to form a barrier to protect underlying tissue from infection, dehydration, chemicals and mechanical stress.
Ecdysis is the process of an arthropod moulting its exoskeleton. Moulting is necessary as the arthropod exoskeleton is inflexible and so, to grow larger, arthropods must moult.
Hence the correct option is A.