Solution A is hypertonic means:

- Water is drawn out of the cells by this Solution and the cells will shrink (the solution can grab water from the cells).

Solution A is isotonic means:

- There are no net movement of water in or out of the cells and the cells will not change shape (the solution cannot grab water from the cells).

Solution A is hypotonic means:

- Water is drawn inside the cells and the cells will burst (hemolysis) (Not only the solution cannot grab water from the cells, but it is loosing its own water to the cells).
These terms are purely descriptive: they describe what the water is doing. They do not explain at all why water is doing it.
So, do not explain hemolysis of red blood cell by by saying that it is because the solution is hypotonic and leave it at that. It would be like saying: "the cells burst because water enters the cells and make them burst". You have to explain why the water enters the cell. You have to explain why the solution is hypotonic.