Check each statement using a simple true or false test against known quantitative or established environmental engineering facts.
Statement (A): the standard risk formula used across environmental and industrial risk assessment is
\[ R = P \times S \]
where $R$ is risk, $P$ is probability of the hazardous event, and $S$ is severity of the resulting damage. This matches the statement exactly, so (A) is TRUE.
Statement (B): the octanol-water partition coefficient is defined as
\[ K_{OW} = \frac{C_{octanol}}{C_{water}} \]
A large $K_{OW}$ means the chemical concentrates preferentially in the lipid-like octanol phase relative to water, the same behavior it would show partitioning into fatty tissue in a living organism. So a HIGH $K_{OW}$ predicts HIGHER bioaccumulation, not lower. The statement claims the opposite relationship, so (B) is FALSE.
Statement (C): pump and treat systems are defined in groundwater remediation literature as extraction wells pumping contaminated groundwater to the surface, treatment units such as air strippers, GAC, or biological reactors removing the contaminants, and the treated water being returned or discharged. This is textbook contaminated groundwater remediation, so (C) is TRUE.
Statement (D): a single counterexample is enough to falsify an absolute never claim. Bioremediation of petroleum-hydrocarbon-contaminated hazardous waste using hydrocarbon degrading bacteria is a documented, commonly used hazardous waste treatment technique. This counterexample makes the never claim in (D) FALSE.
Collecting the TRUE statements: $\{A, C\}$.
\[\boxed{\text{Answer: (A), (C)}}\]