The missing part of this question is as follow:
Redi placed pieces of meat in several jars. He divided the jars into two groups. He covered the first group of jars with fine cloth. He left the second group of jars uncovered. Redi observed the jars for several days. He saw files on the cloth of the covered jars, and he saw files laying eggs on the meat in the uncovered jars. Maggots appeared only on the meat in the group of jars left uncovered
Answer:
The correct answer is - b. Covering one jar and leaving the other uncovered.
Explanation:
Variable or the factors in an experiment that is subject to change or that affects the particular experiment. In the experiment of F. Redi, he used two groups of jars one covered with fine cloth and the other open and exposed to the environment.
There is a change in the result of the experiment of Redi due to these variables as the jar that was covered has no maggots while maggots appeared in open jar.
