Answer: D) a chemostat using a low-nutrient medium
Explanation:
A chemostat is a bioreactor in which a constant chemical environment is maintained. In the bioreactor the fresh medium is added, whereas the culture liquid, left out nutrients, microorganisms and metabolic end products are removed from the medium at the same rate to keep the volume of the culture constant.
The volume and concentration of the nutrient medium can be maintained in the chemostat bioreactor.
According to the given situation, the bacteria can be cultured in low-nutrient growth medium that is the lake water to observe its adaptation under the low-nutrient concentration.