The origin is greek and English
Answer: TWO.
At least two groups: treatment group and control group.
The treatment group is that is exposed to the different levels of the independent variable ( a medication for example), while the control group is not treated, so the researchers can compare the effect of the medication.
Answer:
A
Explanation:
Combustion reaction always has something hydrocarbon plus oxygen gas which equals to carbon dioxide and water. Always being a reactant in a combustion reaction is oxygen, since reactants are what we start off the reaction with.
