The type of solution that doesn't change the shape of a cell is called an isotonic solution.

Here's why:

* Isotonic: An isotonic solution has the same concentration of solutes (dissolved substances) as the inside of the cell. This means there's no net movement of water across the cell membrane. Since the water balance is maintained, the cell's shape stays the same.

Here's a comparison to other types of solutions:

* Hypotonic: A hypotonic solution has a lower concentration of solutes than the inside of the cell. Water moves into the cell to try and balance the concentrations, causing the cell to swell and potentially burst (lysis).

* Hypertonic: A hypertonic solution has a higher concentration of solutes than the inside of the cell. Water moves out of the cell to try and balance the concentrations, causing the cell to shrink (crenation).

In summary: An isotonic solution maintains the cell's shape because there is no net movement of water across the cell membrane.