The body of an insect is covered by a protective __________________ formed from chitin and protein. Depending upon its precise composition and thickness, the cuticle may be soft and flexible or hard and rigid; according to requirements, it may or may not be permeable or waterproof:
A. three-layered skin (cuticle)
B. Two-layered skin (cuticle)
C. Six- layered skin (cuticle)
D. None of the above