The correct answer is D. Epidermis.
The epidermis is the outermost layer of cells in an animal’s body. It is made up of a single layer of cells that are constantly being shed and replaced. The epidermis is responsible for secreting the cuticle, which is a hard, protective layer that covers the arthropod’s body.
The endodermis is the innermost layer of cells in the root of a plant. It is responsible for regulating the movement of water and nutrients from the soil into the plant.
The mesophyll is the middle layer of cells in a plant leaf. It is responsible for photosynthesis, the process by which plants use sunlight to convert carbon dioxide and water into glucose and oxygen.
Chitin is a long-chain polymer of N-acetylglucosamine, a type of sugar. It is the main component of the arthropod’s exoskeleton, which is the hard outer covering that protects the animal’s body.