Q12. In an experiment with a particular bacterial species, you plate 100 samples in separate petri dishes. Half of these, group A, have all necessary nutrients, while group B have low levels of one important nutrient. All petri dishes are placed in an incubator and are treated identically. After several weeks, you measure colony growth and find that the colonies in group B are, on average, 4 mm smaller in diameter than those in group A. What is the most reasonable explanation? * *