Cumulative Toxicity

Step 1: Understanding Bioaccumulation and Biomagnification.
Bioaccumulation refers to the process by which an organism accumulates toxic substances in its body over time due to continuous exposure to pollutants in its environment (e.g., water, food, air).
Biomagnification refers to the increase in concentration of pollutants as they move up the food chain. Higher-order organisms (e.g., predators) accumulate higher concentrations of pollutants than lower-order organisms (e.g., prey).

Step 2: Analyzing the options.

(A) Bioaccumulation is the process by which a living organism keeps on accumulating pollutants in its body due to continuous exposure, whereas, bio-magnification is the process by which higher order organisms accumulate more pollutants than the lower order organisms in a food chain.
This is correct. Bioaccumulation occurs at the individual level, while biomagnification occurs at the ecosystem level through the food chain.

(B) Biomagnification is the process by which a living organism keeps on accumulating pollutants in its body due to continuous exposure, whereas, bioaccumulation is the process by which higher order organisms accumulate more pollutants than the lower order organisms in a food chain.
This is incorrect because biomagnification refers to the increase in pollutant concentrations as one moves up the food chain, not to the accumulation in an individual organism.

(C) Bioaccumulation and biomagnification are possible with heavy metals, but not with pesticides and pharmaceutical compounds.
This is incorrect because both bioaccumulation and biomagnification are possible with a variety of substances, including pesticides and pharmaceutical compounds, not just heavy metals.

(D) Bioaccumulation and biomagnification are possible with heavy metals, pesticides and pharmaceutical compounds.
This is correct. These processes can occur with a wide range of toxic substances, including heavy metals, pesticides, and pharmaceutical compounds.

Thus, the correct answers are (A) and (D).