An experiment is performed to study how the change in some variables affects other related variables.
I can't see the diagrams but I can give you general answers for each statement.
1) We define a good experiment as an experiment where only one variable is tested at the time, this is because this allows the scientists to isolate the impact of that variable in the experiment.
"Since only one variable was changed in this experiment, this is called a good experiment."
2) The independent variable is the variable that the scientists can change in an experiment, in this case, we know that she does change the hours of light that each plant gets, so we can conclude that the independent variable is the time of light exposition that each plant gets.
"The independent variable in this experiment is the time of light exposition"
3) The dependent variable in an experiment is the variable that reacts to the changes in the independent variable, it usually is the thing that the scientist wants to study. In this case, we know that she is studying the floration times of tobacco plants, so:
"The dependent variable in this experiment is the flowering time of tobacco plants"
4) Controlled variables are, in principle, independent variables, that are fixed for the whole experiment. We can't see the controlled variables because there are no graphs, but we can think about what we should fix in this type of experiment.
The temperature: All the plants should grow in the same temperature, as it can affect the flowering times.
The humidity: The humidity also could impact on the flowering of the plants, so we need to fix it for the 5 plants.
The strain: All 5 tobacco plants need to be from the same genetics, we know that different genetics from different parts of the world may react differently to changes in light or temperature, so the strains need to be equal.
Substrates: All the plants should be on the same substrate, so she can be sure that all the plants are getting exactly the same nutrients from the soil.
These are just some examples, if you were designing this experiment, you would see that there are a lot of variables that need to be controlled.
If you want to learn more, you can read:
https://brainly.com/question/1479694
