Knowledge on diffusion and osmosis is key in this question. Diffusion is the movement of substances from a high concentration to a low concentration while osmosis is the movement of water molecules down a concentration gradient across a semipermeable membrane from a region with high concentration of water molecules to low concentration. In this case, the dialysis bag is hyper and the movement of water molecules in and out of the dialysis bag is purely osmosis. Therefore, one would gain weight. The best representation of IV fluid for human cells is normal saline solution.