Final answer:
The answer to your question is b) Epidermis. It is the outermost layer of skin, significantly thicker on the palms and soles due to an additional fifth layer, providing extra protection against stress.
Step-by-step explanation:
The epidermis is the outermost layer of skin in mammals and is known for its protective function against environmental factors. It varies in thickness across different parts of the body, with it being the thinnest on the eyelids and the thickest on the palms of the hands and soles of the feet. Direct answer to the student's question: b) Epidermis. This outer layer of skin, composed primarily of keratinocytes, increases in thickness as an adaptive response to the friction and pressure experienced in these areas.
The epidermis on the hands and feet has an additional fifth layer, called the stratum lucidum, between the stratum granulosum and stratum corneum, which contributes to its increased thickness, making the epidermis much thicker on the palms and soles compared to its thinner counterpart covering the rest of the body.