The correct option is
B (p) - (ii), (q) - (iv), (r) - (i), (s) - (iii)
(p) Cytology-(ii)-Study of cells-Cytology is a branch of biology that studies the structure and function of the cell, which is the basic unit of life. It is also called cell biology.
q) Entomology-(iv)Study of insects-Entomology is the scientific study of insects, a branch of zoology. Entomology is a taxon-based category; any form of scientific study in which there is a focus on insect-related inquiries.
(r) Palaeontology-(i)Study of fossils-Palaeontology is the study of fossils to determine organisms' evolution and interactions with each other and their environment.
(s) Ornithology-(iii)Study of birds-Ornithology is a branch of zoology that concerns the study of birds. It is principally concerned with descriptions and distributions of species.