Answer : 1. "Around 120 days "
Explanation :

1. The average life of red blood cells in the human body is 120 days. This is the time it takes from the formation of red blood cells until they flow in the blood. Red blood cells are made in the bone marrow and then they are shed into the blood. While flowing in the blood, red blood cells carry oxygen from the lungs to the rest of the body and carry carbon dioxide from the rest of the body to the lungs.