In an experimental design, the variable the
researcher has control over and that is different for the treatment and control
groups is called the explanatory variable.
The explanatory variable can be controlled and
manipulated by the experimenter.
The correct answer between all
the choices given is the last choice or letter E. I am hoping that this answer
has satisfied your query and it will be able to help you in your endeavor, and
if you would like, feel free to ask another question.
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For questions four plants make their own food which is oxygen gas. This oxygen gas, is an important part of the air, the gas that plants and animals must live on. When people breathe, it is oxygen that we take out of the air to keep our cells and bodies alive.
I would say D.....................
