Colouration of the skin depends on-

Correct Answer: D

Rationale: The correct answer is D, "All of the above." The colouration of the skin depends on the amount of blood in its blood vessels (A), as blood vessels can give the skin a pink or red hue. The inherent yellowish colour of its tissue (B) also contributes to skin colour, especially in lighter skin tones. Additionally, the amount of melanin in its tissue (C) plays a significant role in determining skin colour, with more melanin leading to darker skin tones. Therefore, all of these factors collectively influence the colouration of the skin, making option D the correct answer.

Correct Answer: A

Rationale: The correct answer is A because sebaceous glands secrete sebum, an oily substance that lubricates the hair and skin, making them waterproof. Sebum also helps protect the skin from drying out and maintains its elasticity. Choice B is incorrect because sebum doesn't make the hair waterproof on its own. Choice C is incorrect because sebum also affects the skin, not just the hair. Choice D is incorrect as sebum plays a crucial role in skin and hair health.

Correct Answer: A

Rationale: The correct answer is A: Rhinoceros. Rhinoceros is the only animal among the options that has sweat glands only on its pinnae (ears). The other choices, Deer, Hippopotamus, and Rabbit, have sweat glands distributed throughout their bodies or in different areas, not just on the pinnae. This unique anatomical feature of the Rhinoceros helps it regulate body temperature by cooling the blood vessels around the ears. Therefore, Rhinoceros is the correct answer based on the specific location of its sweat glands.

Correct Answer: D

Rationale: The correct answer is D: Stratum corneum. This layer of skin is water-proof due to the presence of keratin, a protein that forms a protective barrier against water loss and external substances. The other choices, A, B, and C, do not have the same water-proofing properties. Stratum germinativum is the innermost layer responsible for cell division, stratum granulosum is involved in keratin production, and stratum lucidum is a thin, translucent layer found only in thick skin areas. Therefore, only the stratum corneum contains the necessary structures to make it water-proof, making it the correct choice.

Correct Answer: C

Rationale: The correct answer is C because the dermis is the layer of skin that provides strength, flexibility, and elasticity, making it suitable for shoe leather. Choice A is incorrect because the presence of cells alone doesn't determine leather quality. Choice B is incorrect as hardness is not a desirable quality for shoe leather. Choice D is incorrect as ecdysis refers to the shedding of skin by animals, not the process of obtaining leather.