Question

what are stacks of thylakoids called? mesosomes cellular matrix grana

Explanation:

In biology (a subfield of Natural Science), thylakoids are membrane - bound structures in chloroplasts. Stacks of thylakoids are known as grana. Mesosomes are structures in prokaryotic cells, and cellular matrix is not related to thylakoid stacks.

Answer:

grana (the option with "grana" text)