Match List - I with List - II and choose the correct answer.

List - I		List - II
(a)	Cristae	(i)	Primary constriction in chromosome
(b)	Thylakoids	(ii)	Disc-shaped in Golgi apparatus
(c)	Centromere	(iii)	Infoldings in mitochondria
(d)	Cisternae	(iv)	Flattened membranous sacs in stroma of plastids

The correct option is: a - (iii) b - (iv) c - (i) d - (ii).

Let us understand the structure and functions of each cellular component listed in List - I and match them with their description in List - II:

(a) Cristae:
Cristae are the characteristic infoldings of the inner mitochondrial membrane. These folds greatly increase the surface area available for the chemical reactions of cellular respiration (specifically, the electron transport chain and ATP synthesis).
⇒ Therefore, a matches with (iii).

(b) Thylakoids:
Thylakoids are flattened, membranous sacs found within the stroma of chloroplasts (which are a type of plastid). They contain chlorophyll and are the site where the light-dependent reactions of photosynthesis take place.
⇒ Therefore, b matches with (iv).

(c) Centromere:
The centromere is the primary constriction region in a chromosome. It holds sister chromatids together and serves as the site for spindle fiber attachment during cell division (via the kinetochore).
⇒ Therefore, c matches with (i).

(d) Cisternae:
Cisternae are flat, disc-shaped, membrane-bound sacs that are stacked parallel to each other to make up the Golgi apparatus. They are involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.
⇒ Therefore, d matches with (ii).

Combining these individual matches, we get:
a - (iii), b - (iv), c - (i), d - (ii).