ANS:C - 90°

The correct angle for maximum discharge over a triangular notch is 90°. When the notch angle is 90 degrees, it means that the notch is rectangular, not triangular. For a rectangular notch, the angle at the vertex (notch angle) is indeed 90 degrees, and it allows for the maximum discharge for a given head. In a rectangular notch, the width is usually much larger compared to other types of notches, which allows for a larger opening and more efficient discharge of water. Additionally, the rectangular shape provides better flow characteristics, resulting in the maximum possible discharge for a given head. Therefore, the correct answer for the notch angle for maximum discharge over a triangular notch is 90° (rectangular notch), not 60°. Thank you for bringing this to my attention.