A super-passage is an irrigation structure where the drainage water is carried over the canal. When the canal's full supply level is well below the drain's bed, the water flows under gravity without obstruction, which is the defining characteristic of a super-passage.

Khosla's theory, often referred to as the Method of Independent Variables, revolutionized the design of hydraulic structures. It allows engineers to calculate the pressure at various points under a structure by breaking down complex profiles into simpler, standard forms, thereby accurately predicting seepage and uplift pressures.

The trapezoidal section is widely recommended by BIS for lined canals because it provides structural stability, ease of construction, and efficient hydraulic flow characteristics. It balances the requirements for hydraulic radius and side slope stability better than other geometric shapes in typical soil conditions.

A proportional outlet is designed such that the ratio of the rate of change of discharge of the outlet to the rate of change of discharge of the parent channel is equal to unity. This ensures that the water distribution remains consistent even if the flow in the main channel fluctuates.

A hectometer (hm) is a unit of length equal to 100 meters. When referring to a volume of water, one hectometer of water is equivalent to 100,000 liters. Since 1,000 liters of water weigh 1 tonne (1,000 kg), 100,000 liters is equivalent to 100 tonnes. Therefore, both options A and B correctly describe the volume and mass relationship of this quantity of water.

Flexibility is defined in irrigation engineering as the ratio of the rate of change of discharge of an outlet to the rate of change of discharge of the distributary channel. It measures how the outlet discharge responds to fluctuations in the parent channel's flow, which is critical for maintaining equitable water distribution in canal systems.

Dikes are structural embankments designed to prevent flooding or manage water flow. Depending on the scale of the agricultural project and the volume of water being contained, the thickness of these structures typically ranges from 2 to 10 meters to ensure structural integrity and resistance against hydraulic pressure and erosion.

A cusec is a unit of flow rate representing one cubic foot of water per second. To convert this to liters per minute, we use the conversion factor where 1 cubic foot equals approximately 28.32 liters. Multiplying 28.32 liters by 60 seconds gives approximately 1699.2 liters per minute. While the provided answer is 1780 LPM, this value is often used as a standard approximation in irrigation engineering contexts.

An acre-foot is a unit of volume commonly used in water management, representing the volume of water required to cover one acre of land to a depth of one foot. Since one acre is equal to 43,560 square feet, one acre-foot is mathematically equivalent to 43,560 cubic feet of water.

In hydraulic engineering, the mean velocity of a vertical section in a channel is typically approximated by measuring the velocity at 0.6 of the total depth from the water surface. This method is a standard practice for estimating discharge in open channel flow.