This question was poorly attempted by the candidates.  In 4(a-b), most of the candidates could neither describe the activities involved in earthen pond construction nor explain pond maintenance activities.
The expected answers include:
4 (a) Activities involved in earthen pond construction
                  -     Clearing: clear the pond area of all vegetation, debris, stones, stumps, trees, grass
                  -     Marking/pegging: mark the area for excavation with stakes indicating depth
                        Of cut from the ground surface to the pond bottom
                  -     Demarcation: demarcate the base of the pond by pegging within the first marked areas (toe stake) and then the outer area (top width stake) depending on the size of the pond under construction
                  -     Determine the gradient and mark out the water inlet and outlet
                  -     Completely remove top soil and set aside
                  -     Start digging from the outlet inside the inner marked stakes
                  -     Build walls using loam or silt clay soil
                  -     Installation of drains, core trench, spillway, inlet pipes, freeboard
                  -     Compact walls at every 15-20cm layer to strengthen embankment to avoid collapse when impounded with water
                  -     Pond bottom should slope towards outlet/drain
                  -     Both inlets and outlets should be properly screened
                  -     Plant grasses on dam to protect pond from erosion
                  -     Provide diversion ditch to protect pond from flood         
(b)  Pond maintenance activities
                  -      Flushing of pond to reduce turbidity
                  -      Liming to regulate water pH/control predators, reduce silt and clay particles
                  -      Fertilization provides nutrients to increase natural fish food
                  -      Repair of leakages to reduce water seepage
                  -      Cleaning pond debris to reduce siltation/enhance easy movement of fish/ enhance harvesting of fish
                  -      Weeding to reduce predators
                  -      Cleaning of filters/screen for easy flow of water