Blood for essential blood!

Blood represents 7 to 8% of body weight and, by volume, between 4 and 6 liters. There are eight blood types: A+, A-, B+, B-, AB+, AB-, 0+, 0-, with the Rh factor +/- [Rh] determining whether the group is positive or negative. The O- group is the only compatible one for everyone, also called the "universal donor." The hemoglobin contained in red blood cells gives blood its red color and ensures the transport of oxygen (O2) to the body.