The correct option is C Stroma of thylakoid
Ferredoxin (Fd) is a small, water soluble protein present in the stroma of the thylakoid. It may be sometimes present in the membrane of thylakoid but is usually found in the stroma. It is a mobile protein and can move through the stroma. It accepts electrons from Fe-S centres and transfers them to ferredoxin-NADP+-reductase (FNR).