4. Which of the following statements is true about the Thomas Slope Method for Statistical determination of ultimate BOD, Lo, and biodegradation rate coefficient, k : (8pts) A. It is based on the simplified form of the convergent Taylor Series for the term Lo(1ekt) B. It is based on the second derivative of the BOD removal term Lo(1ekt) which yield the termLs[kt(1+6kt)3] C. It is based on the simplified form of the convergent Taylor Series for the term Lo[kt(1+6kt)3] D. The series for the BOD term Lo(1ekt) and the term Lo[kt(1+6kt)3] are equal up to the third term, thus the latter term can be used to calculate BOD as a function of time. 5. Explain why removal rates for both conservative and non-conservative substances in natural water bodies is assumed to follow first-order decay rate kinetics. Indicate the risks posed by the over-reliance on the first-order kinetic model in a broad range of scenarios. (8pts)