ANSWER:
Iron is the mineral that transports oxygen in the blood.
EXPLANATION:
Iron is found in the "red blood cells" of the body as well as in the "muscle cells" and is called myoglobin.
Haemoglobin is essentially the iron present in the red blood cells and carries oxygen from lungs to the tissues. The "myoglobin in the muscle cells" accepts, stores and transports oxygen in the body. Iron also gives blood its red color.