Most bacteria live in a solution that is hypotonic relative to the cytoplasm of the bacteria. This means that the bacterial cell is constantly taking in water. The cell wall of a bacterium is a peptidoglycan polymer that is tightly cross-linked. This would therefore function to:-.

Provide rigidity to the bacterial cell

Explanation:

The bacteria possess a cell wall composed of peptidoglycan molecule formed by the amino acids called murine.  The bacterial cell wall helps in the survival of the bacteria in some extreme condition like when placed in a hypotonic solution.

The hypotonic solution is formed when it has low solute concentration and high water amount when compared. When the bacterial cell will be placed in hypotonic solution then the water will move inside the cell down the concentration gradient as a result of which the bacterial cell will swell but will not burst.

This happens as the cell wall contains expansin protein which allows the cell wall to expand and provides rigidity to the cell.

Thus, Provide rigidity to the bacterial cell is the correct answer.