After Reading the Paragraphs Below, Answer the Question(s) That Follow(s)

Multiple Choice

After reading the paragraphs below, answer the question(s) that follow(s) .
In the 1930s, the Navajo nation treated sheep and cattle for ticks and other parasites by using concrete "dip tanks." Animals were herded through one end of the tank and out the other. Each day, the tanks were filled with 200 000 gallons of insecticide and any remaining chemicals were emptied onto the ground. The pesticide solution seeped into the ground, ditches, and pits around the tanks. This was a common practice in the United States during that period.
The EPA Emergency Response Team (ERT) was called to the Navajo nation during the 1990s to investigate. They concluded that bioremediation procedures were the best for this site. Certain types of bacteria are able to feed on and digest toxic organic substances, such as pesticides, and use them as fuel for cell respiration. The ERT distributed the pesticide-eating microorganisms through the contaminated soil to remove the chemical residues. Once the contaminants are degraded, these microorganism populations die off because they've used all of their food supply.
-There are some possible problems associated with the approach detailed above. Which of the following does not describe a potential environmental risk?

A) The bacteria used to decontaminate the affected soil could evolve into something harmful that persists after the initial problem has been solved.
B) The bacteria used to decontaminate the affected soil could outcompete and eliminate other beneficial bacteria within the soil.
C) The bacteria used to decontaminate the affected soil could partially degrade the toxic material, leaving different toxic material.
D) The bacteria used to decontaminate the affected soil could need to be reapplied continually.