B.

G₁ - S - G₂ - M

The complete cell cycle contains a sequence of phases which are

(a) Interphase which is further subdivided into G₁-phase or postmitotic gap, S-phase or synthesis phase and G₂-phase or premitotic gap respectively 

(b) Dividing phase or M-phase (mitotic or meiotic phase) which comprises karyokinesis and cytokinesis.

So, the correct sequence of phases in cell cycle is

G₁ $\to$S $\to$G₂ $\to$M

D.

Cohort

Cohort is a formal taxonomic category in between infra- class and super- order in plant kingdom but not in animals.

Class $\to$Sub Class $\to$Infra Class $\to$Cohort $\to$Super Order $\to$Order

A.

coronary artery

Coronary arteries are the blood vessels that supply the heart muscle (cardiac tissue) with blood rich in oxygen.

Coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the heart muscle. It carries less oxygenated blood to the right atrium as do the superior and inferior vena cavae.

Pulmonary veins are the veins that transfer oxygenated blood from the lungs to the heart. The largest pulmonary veins are the four main pulmonary veins, two from each lung that drain into the left atrium of the heart.

A.

mixed X cranial nerve

Vagus nerve is the tenth cranial nerve of mixed nature. It innervates to the chest, abdomen and heart.

D.

31 pairs

Man has 31 pairs of spinal nerves. These are

(a) Cervical 8 pairs in neck
(b) Thoracic- 12 pairs in thorax
(c) Lumbar- 5 pairs in upper part of abdomen
(d) Sacral 5 pairs in lower part of abdomen
(e) Coccygeal tail nerve.

Frog has 10 pairs of spinal nerves, while rabbit has 37 pairs of spinal nerves.