The most suitable material for a sewer for carrying storm water is

ANS:D - cement concrete

The most suitable material for a sewer for carrying stormwater is cement concrete. Cement concrete pipes are commonly used for stormwater drainage systems due to their durability, resistance to corrosion, and ability to withstand high flow rates and varying weather conditions. Concrete pipes have a long service life and are relatively low in cost compared to other materials. They also provide smooth internal surfaces, which minimize the risk of blockages and sediment buildup, ensuring efficient flow of stormwater. While other materials like asbestos cement, cast iron, and mild steel may also be used for sewer systems, cement concrete is often preferred for stormwater sewers due to its favorable properties and cost-effectiveness.