Name four clastic sedimentary rocks and explain how these rocks form

Limestone: it can form organically from the accumulation of shell, coral,and fecal debris. It can also form chemically from the precipitation of calcium carbonate from lake or ocean water. 
Breccia: Composed of large fragments and the spaces between the fragments are filled with smaller pieces and mineral cement
Rock Salt: forms from the evaporation of ocean or saline lake waters.
Sandstone: forms from sand size weathering debris in environments where large amounts of sand can accumulate include beaches, deserts, flood plains and deltas.

The problem of malnutrition in bangladesh is caused in part by "over population."hope my answer has you : )