The best answer is b - it is rigid.
The cell wall is defined as the rigid, outermost layer found in plants and also certain bacteria, algae and fungi. It is absent in animal cells.
The plant cell wall is made up cellulose which is a structural carbohydrate. The cell wall is rigid and thus offers structural support allowing plant such as trees to grow to great heights.
It also helps prevent water loss, helps protect against insects and pathogens and keeps the shape of the plant.