The correct answer is: Haemoglobin.
Haemoglobin is a protein found in red blood cells that carries oxygen from the lungs to the rest of the body. It is made up of four subunits, each of which contains a heme group. The heme group is a complex of iron and protoporphyrin IX, which is a ring-shaped molecule with four nitrogen atoms. The iron atom in the heme group can bind to oxygen, and when it does, the blood turns red.
Cytochrome is a protein that is found in all cells. It is involved in the electron transport chain, which is a series of reactions that produce ATP, the energy currency of the cell. Cytochromes are not red in color.
Chlorophyll is a green pigment that is found in plants. It is responsible for absorbing sunlight and using it to produce food. Chlorophyll is not red in color.
Hemocyanin is a copper-containing protein that is found in the blood of some invertebrates, such as mollusks and crustaceans. It carries oxygen in the blood, and it is blue in color.
Therefore, the correct answer is: Haemoglobin.