Which of the following is part of cytochrome?

The correct option is B Fe
Cytochromes are iron containing heme proteins central to which are heme groups that are primarily responsible for the generation of ATP via electron transport. For many cytochromes, the metal ion present is that of iron, which interconverts between Fe${}^{2+}$ (reduced) and Fe${}^{3+}$ (oxidized) states (electron-transfer processes) or between Fe${}^{2+}$ (reduced) and Fe${}^{3+}$ (formal, oxidized) states (oxidative processes). Cytochromes are, thus, capable of performing oxidation and reduction.