D is the answer of transportation
1) receptor proteins need to b on the outside of a cell so the cell can absorb the nutrients it needs. receptors have a specific job, membranes are semi-permeable meaning it doesn't absorb nutrients that are not needed 4 a cell to function in a healthy individual.
2) water and glucose are what most cells need to produce energy to function and produce ATP, which allows the bloodstream to deliver nutrients to the entire body.
I am certain that it is due to the rotation of Earth. Note that earth rotates at almost a 1000mph.