Match List-I with List-II and choose the correct answer from the options given below.

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

We need to pair each structure in List‑I with its correct description in List‑II.

(a) Cristae – These are the deep infoldings of the inner mitochondrial membrane. In the list of descriptions, this corresponds to (iii) “Infoldings in mitochondria”.

(b) Thylakoids – In chloroplasts, thylakoids are the flattened membranous sacs (or discs) that lie within the stroma. The matching description is (iv) “Flattened membranous sacs in stroma of plastids”.

(c) Centromere – The centromere is the region of a chromosome where the primary constriction occurs, allowing sister chromatids to attach to spindle fibers during cell division. This matches (i) “Primary constriction in chromosome”.

(d) Cisternae – Cisternae are the disc‑shaped membrane‑bound sacs of the Golgi apparatus. The appropriate description is (ii) “Disc‑shaped sacs in Golgi apparatus”.

Thus the correct matching is:

a – iii,  b – iv,  c – i,  d – ii