Red cells contain a special protein called hemoglobin, which helps carry oxygen from the lungs to the rest of the body and then returns carbon dioxide from the body to the lungs so it can be exhaled. Blood appears red because of the large number of red blood cells, which get their color from the hemoglobin.
The period is the time it takes the satellite to make a complete orbit around the central object. As the distance increases, so does the period because the orbit becomes longer because the radius increases.
