The maximum depth of sedimentation tanks, is kept

ANS:A - 3 m

The maximum depth of sedimentation tanks can vary depending on various factors such as the design standards, treatment requirements, and engineering considerations. However, a common depth for sedimentation tanks in wastewater treatment plants is typically around 3 to 4 meters (9.8 to 13.1 feet). Given the options provided:

• 3 m (approximately 9.8 feet)
• 3.5 m (approximately 11.5 feet)
• 4 m (approximately 13.1 feet)
• 4.5 m (approximately 14.8 feet)

Among these options, a depth of 3.5 meters (11.5 feet) or 4 meters (13.1 feet) seems plausible for a maximum depth of sedimentation tanks in a wastewater treatment plant. However, without additional context or specific design requirements, it's challenging to determine the exact depth.