The correct answer is B. (i) and (ii).
A septic tank is a tank that receives wastewater from a home or business and separates the solids from the liquids. The solids settle to the bottom of the tank, where they are broken down by bacteria. The liquids flow out of the tank and into a drain field, where they are further treated by soil bacteria.
A septic tank is a settling tank because it allows the solids to settle to the bottom. The solids are then broken down by bacteria, which is a form of digestion. The liquids flow out of the tank and into a drain field, where they are further treated by soil bacteria.
A septic tank is not an aeration tank. An aeration tank is a tank that is used to treat wastewater by adding air. The air helps to break down the solids and to remove bacteria. Septic tanks do not have aeration tanks.
I hope this helps! Let me know if you have any other questions.