Agroup of biology students tests the growth of bacteria under different conditions. the students apply the same amount of bacteria to identical petri dishes enriched with nutrients, then place each plate at a different temperature. the bacteria are allowed to grow for three days, after which the number of bacterial colonies on each plate is counted. what is the dependent variable in this experiment? a. the temperature at which the colonies grew b. the number of bacterial colonies after three days c. the nutrient type present in the petri dishes d. the time of day that the experiment is performed