Answer: Cornea
Explanation: The cornea is the only part of a human body that has no blood supply as it gets oxygen directly through the air.
Lifting the backpack off the floor. Force is being applied in only one direction then (up) which is what constitutes as work. Carrying the box of crayons applies force in two directions (up and forward), which cancel each other out. Work has a vector, which is a quantity containing both direction and magnitude (one, finite direction, not two).
