Final answer:
To protect a sewer system from flooding, it is important to install flood gates, implement a drainage system, and regularly inspect and maintain the system. Option 4.
Step-by-step explanation:
Protecting a sewer system from flooding involves implementing several measures:
- Installing flood gates at the sewer entrances: Flood gates can be installed at the entrances of the sewer system to prevent floodwater from entering.
- Implementing a proper drainage system: A well-designed drainage system can help divert excess water away from the sewer system, reducing the risk of flooding.
- Regularly inspecting and maintaining the sewer system: Regular inspections and maintenance can help identify and address any issues that may lead to flooding, such as blockages or structural damage.
Therefore, the correct answer is option 4) All of the above as all these measures are necessary to protect a sewer system from flooding.