B.

Cartilage is usually described as a vascular, as the blood vessels innervate only the outer fibrous sheath of cartilage, called perichondrium. The cornea is the transparent anterior portion of the outer coat of the vertebrate eye covering the iris and the pupil. It is avascular as it lacks lymphatic and blood vessels.

D.

Nitrogenase is insensitive to oxygen

Root nodules of leguminous plants harbour symbiotic bacteria, Rhizobium, which fixes atmospheric nitrogen and provides the plant with most or all of its nitrogen requirements. In return, they have access to a rich supply of carbohydrate. The fixation of atmospheric nitrogen (N₂) to ammonia (NH₃) occurs within the nodules, using the enzyme nitrogen cut this enzyme is very sensitive to oxygen and gets inhibited in oxygen rich environment. This problem is solved by leghaemoglobin, a pinkish-red, oxygen-binding, iron-containing protein present in root nodules. It functions as oxygen buffer, scavenges oxygen and provides the enzyme nitrogenase, a low oxygen environment in which nitrogen fixation can occur.

A.

Opunita

opuntia is a plant growing in dry and xeric habitats.In this, the stem, having several nodes and internodes is modified into flat, fleshy, thick green,  leaf-like structure called phylloclades. Phylloclade performs the function of photosynthesis like a leaf and also stores food leaves get modified into spines which help to reduce transpiration.

B.

Earthworm -Pharyngeal, integumentary and septal nephridia

In earthworm, the excretory system is made up of many segmentally arranged microscopic coiled tubes called nephridia. These are ectodermal in origin and analogous to the vertebrate kidney.
In Pheretima, following three types of nephridia are seen.
(i) Pharyngeal nephridia - Situated on either side of pharynx and oesophagus in 4, 5 and 6 segments.
(ii) Integumentary nephridia - Scattered in the body wall, seen from 7th segment onwards
(iii) Septal nephridia - Largest nephridia attached to both faces of each intersegment septum behind 15th segment

D.

Proteins will not be adequately hydrolyzed by pepsin into proteoses and peptones

The parietal cells or oxyntic cells are large, rounded cells located upon the surface of gastric glands. These cells secrete HCl (which converts inactive pepsinogen into active pepsin) and Castle's Intrinsic Factor of CIF (which helps in the absorption of vitamin -B₁₂ or cyanocobalamine). If somehow, parietal cells become partially non-functional, the patient will suffer from achlorhydria (no HCl) or hypochlorhydria (less HCl).This will result in the non- activation of pepsinogen due to which proteins will not be adequately hydrolysed into proteoses and peptones. Lack of CIF will cause vitamin-B₁₂ deficiency, which will result in pernicious anaemia.