What protein in human blood transports oxygen?

Hemoglobin

What hero killed the Lernean Hydra? What sweet spread made from ground peanuts is popular in sandwiches worldwide? Who composed "Pictures at an Exhibition"? Who created the android known as the Human Torch in Marvel’s Golden Age comics? Who was known as "The Wizard of Menlo Park" for numerous inventions including the phonograph and the incandescent light bulb?