The correct answer is: A. An aqueduct
An aqueduct is a bridge that carries water across a valley, road, or other obstacle. It is a structure that conveys water in an artificial channel, especially over a long distance. Aqueducts are typically used to transport water for drinking, irrigation, or industrial purposes.
A syphon is a pipe or tube that carries a fluid under pressure from a higher level to a lower level. Syphons are often used to drain water from a tank or reservoir.
A level crossing is a type of intersection where a road crosses a railway line at the same level. Level crossings are typically controlled by traffic lights or gates.
An inlet is an opening that allows water to flow into a system, such as a canal or a drainage system. An outlet is an opening that allows water to flow out of a system.
In the case of a canal and a drainage approach each other at the same level, the structure so provided is an aqueduct. This is because an aqueduct is a structure that is specifically designed to carry water across an obstacle, such as a valley or a road. A syphon, level crossing, or inlet and outlet would not be suitable in this situation.