Answer:
B. the number of bacterial colonies after three days
Step-by-step explanation:
As you may already know, a scientific experiment is composed of dependent and independent variables, being necessary that you know how to recognize each one of them.
In summary, an independent variable is one that influences a situation to happen, it influences another variable and it is not necessary to suffer any influence to cause a result. The dependent variable, on the other hand, is influenced by the independent variable and needs that influence to demonstrate a result.
As we saw in the experiment above, the students applied the same amount of bacteria to identical Petri dishes enriched with nutrients and put each plate at a different temperature. This temperature will influence the growth of bacteria for three days. Thus, we can conclude that temperature is the independent variable, while the growth of bacterial colonies is the dependent variable.