The chitinous exoskeleton of arthropods are formed by polymerisation of-
a. Lipoglycans
b. Keratin sulphate and chondroitin sulphate
c. D- glucosamine
d. N-acetyl glucosamine

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Hint: Animal exoskeletons are non-living, made of chitin and calcium carbonate, supporting the body of the animal and defending the organism from predators, water and drying out.

Complete answer:
> Option A is incorrect. Lipoglycans (Lipopolysaccharides; LPS) is the main component of Gram-negative bacteria's outer membrane, contributing greatly to the bacteria's structural integrity, and shielding the membrane from many kinds of chemical assault. Also, LPS raises the cell membrane's negative charge and helps stabilise the membrane structure besides.

> Option B is incorrect. Keratin sulphate is formed by corneal keratocytes, and a complex buffer of corneal hydration is thought to play a part. Sulphate chondroitin has many roles. It primarily provides the joint cartilage with nutrients, helps prevent the enzymes that decompose the joint cartilage, and accelerates the development of new joint cartilage.

> Option C is incorrect. D- glucosamine is a common nutritional supplement and natural cartilage component that is often combined with chondroitin sulphate and used for osteoarthritis and non-specific pain in the joints. In humans, it occurs as a component of hyaluronic acid in the skin, cartilage, and blood vessels and as a component of keratan sulphate in the bone tissue, cornea, and aorta.

> Option D is correct. Arthropods exoskeleton is formed by N-acetyl glucosamine polymerisation, which is a glucose derivative. It is also a characteristic feature of the fungi cell wall, mollusc radulae, and cephalopod beaks and inner shells like squid and octopus.

Hence, The correct answer is option (D).

Note: Exoskeletons provide improved muscle strength and protective insulation for muscles and internal organs, as well as increased flexibility during the moulting process, and are restrictive in size and weight.