The color of blood is red due to __________?

A. Haemoglobin
B. Neutrophils
C. Esinophils
D. Hematocrit

Human blood is red because hemoglobin, which is carried in the blood and functions to transport oxygen, is iron-rich and red in color. Octopuses and horseshoe crabs have blue blood. This is because the protein transporting oxygen in their blood, hemocyanin, is actually blue