ANS:D - all the above.

1. Kinchling: There is no known figure or concept named "Kinchling" in hydrology or engineering related to runoff estimation or the rational formula. It seems to be a fictitious or misspelled name.
2. Lloyd Davis: Lloyd Davis is a significant figure in the field of hydrology. He is credited with the development of the rational formula for estimating peak runoff. This formula, represented as Q = 0.0278 KpA, where Q is the peak runoff, K is the runoff coefficient, p is the rainfall intensity, and A is the catchment area, is widely used in engineering and hydrological studies for estimating peak runoff rates from urban and rural drainage basins.
3. Frubling: Similar to "Kinchling," there is no known figure or concept named "Frubling" in the context of hydrology or engineering, particularly regarding runoff estimation or the rational formula.