Answer:
Answer here!
Explanation:
One controlled variable can be that they used the same setup, that is the constant between the two experiments. The manipulation was that Spallanzani used a flask without any air and a flask with air. The responding was or the dependent variable was to notice what had changed so in the experiment Spallanzani noticed that the flask with no air led to no microorganisms meaning that the theory of spontaneous generation is false.
