The Streeter-Phelp's oxygen sag equation for a river is based on a few assumptions. The correct assumption$\text{(s)}$ is/are
- At any instant the deoxygenation rate is directly proportional to the amount of oxidizable organic material present
- At any instant the deoxygenation rate is inversely proportional to the amount of oxidizable organic material present
- The reoxygenation rate is directly proportional to the dissolved oxygen deficit
- The reoxygenation rate and deoxygenation rate are directly proportional to the saturation concentration of dissolved oxygen.
