Identify $X$ and $Y$ from the figure.

Match the following columns:-
List-$I$ List-$II$
$(a)$ Cristae $(i)$ Flat membrane-bound sacs in stroma
$(b)$ Cisternae $(ii)$ Infoldings in mitochondria
$(c)$ Thylakoids $(iii)$ Disc-shaped sacs in Golgi apparatus
$(d)$ Kinetochores $(iv)$ Disc-shaped structures in chromosomes

In the given figure,what do the labeled parts 'a' and 'b' represent respectively?

The non-membranous organelles are:

Select the mismatched pair from the following:

Which of the following are single membrane-bound organelles?