The correct option is B They would rupture due to the influx of water.
A blood cell placed in hypotonic solution would gain water as water will enter cell from surrounding hypotonic medium by the process of osmosis causing the cell to swell up. If the cell was placed in hypertonic solution, water would have moved out of the cell causing it to shrink. Red blood cells do not have the cell wall and contractile vacuoles and hence, would not be able to maintain their shape leading to their rupture. Thus, the correct answer is B.