A scientist is investigating cell transport. She observes molecules being transported into a cell through proteins present in the cell membrane. These proteins do not use energy to transport the molecules. Which of the following best explains the type of cell transport observed by the scientist? A. Active transport because membrane proteins were used B. Diffusion because the molecules were entering the cell C. Facilitated diffusion because the proteins were not using energy D. Osmosis because the molecules were moving against the concentration gradient