The correct answer is: C. 200 m
The maximum distance between manholes for large sewers is 200 m. This is to ensure that the sewer can be inspected and cleaned regularly, and to prevent blockages.
Option A: 50 m is too short a distance for large sewers. This would mean that there would be too many manholes, which would be expensive to install and maintain.
Option B: 100 m is a possible distance for large sewers, but it is not the maximum distance.
Option C: 200 m is the maximum distance for large sewers. This is the distance that is recommended by most sewerage authorities.
Option D: 300 m is too long a distance for large sewers. This would mean that the sewer would be difficult to inspect and clean, and there would be a greater risk of blockages.