The most suitable section of a lined canal, is A. Triangular section with circular bottom for small canals B. Trapezoidal section with rounded corners for large canals C. Both (A) and (B) D. None of these

The most suitable section of a lined canal is a trapezoidal section with rounded corners. This is because a trapezoidal section provides the most efficient flow of water, while the rounded corners reduce the risk of erosion.

A triangular section with a circular bottom is not as efficient as a trapezoidal section, as it does not provide as much surface area for the water to flow over. This can lead to the water flowing more slowly and potentially causing erosion.

A trapezoidal section with sharp corners is also not as efficient as a trapezoidal section with rounded corners, as the sharp corners can cause the water to flow more turbulently and potentially cause erosion.

Therefore, the most suitable section of a lined canal is a trapezoidal section with rounded corners.