Environmental pollutants such as PCB's and the pesticide DDT are fat-soluble, non-biodegradable, and contaminate oceans and other aquatic systems. Plankton in the ocean become contaminated by these chemicals and pass them along through the food chain. A pregnant woman has been cautioned to limit her consumption of food that may be high in PCBs. If she consumes food from a nearby contaminated ocean, we would expect that the most contaminated foods would be .

a. fish that eat shrimp.

Explanation:

The PCB's are said to contaminate plankton which then pass them along the food chain including to shrimp which eat plankton. The shrimp will therefore be expected to have higher levels of PCB than plankton because the shrimp eat multiple infected plankton thereby accumulating PCB in their system.

Fish that then eat the shrimp will therefore have even larger amounts of PCB than the shrimp for the same reason as above. Eating the fish would therefore present the most contaminated source to the woman.