C.

If assertion is true but reason is false

Oxysomes or F₀- F_i  particles are present on the inner mitochondrial membrane. The F_i headpiece of oxysome functions as ATP-synthetase which synthesises ATP from ADP and pi (inorganic phosphate) using energy from proton gradient or ATP synthetase becomes active in ATP formation only when there is a proton gradient having high concentration of protons on F₀ side (base) as compared to F_i side (head piece) of F₀- F_i particles or oxysomes.

D.

If both assertion and reason are false.

Pituitary gland or hypophysis is situated in a depression, the sella turcica of sphenoid bone of the skull. It is directly attached to the hypothalamus by a stalk, the infundibulum. Hypophysial portal veins carry blood containing neurohormones (releasing factors) from the hypothalamus to the anterior pituitary. 

C.

If assertion is true but reason is false

Rabies (hydrophobia) is an acute viral disease of the central nervous system that affects all warm-blooded animals and is usually transmitted to humans by a bite from an infected dog. Symptoms appear after an incubation period ranging from 10 days to over a year and include malaise, fever, difficulty in breathing, salivation, periods of intense excitement, and painful muscle spasms of the throat induced by swallowing. In the later stages ofthe disease the mere sight ofwater induces convulsions and paralysis, death occurs within 4-5 days.

C.

If assertion is true but reason is false

Inner ends of cone cells lie upon an elongated, spindle shaped rod, the rhabdome. Rhabdome is secreted and surrounded by a group of seven elongated retinal cells. Rhabdome , and retinal cells together form the receptor region of eye.

B.

environmental resistances

The environmental factors which can check the growth of population size constitute the environmental resistance. These include predators, food, water, nesting sites, similar competitors, etc. All living things tend to reproduce until the point at which their environment becomes a limiting factor. No population, human or otherwise, can grow indefinitely; eventually, some biotic or abiotic variable will begin to limit population growth.