ANS:E - all the above.

1. Only one reading is required: Unlike rectangular notches, which may require multiple readings or adjustments for accurate measurement, a triangular notch often requires only one reading to determine the flow rate accurately.
2. Its formula is simple to remember: The formula to calculate the flow rate through a triangular notch is relatively simple and straightforward, making it easier for operators to remember and use in practice.
3. It gives more accurate results for low discharge: Triangular notches are known to provide more accurate measurements, particularly for low discharge rates, compared to rectangular notches. This is because triangular notches are less prone to measurement errors and disturbances caused by surface tension effects.
4. It measures a wide range of flows accurately: Triangular notches can accurately measure a wide range of flow rates, from low to high, making them versatile and suitable for various flow measurement applications.