The condensation of water vapor formed the early oceans. It is an important part of the water cycle. It is easy to eliminate the other answers in this question. It can't be meteorites, living organisms, or nitrogen.
Answer:
3. Only one independent variable is used for each experiment.
Explanation:
A controlled experiment is an experiment in which one variable is changed or tested at a time, while others are kept constant. In an experiment, one of the two major variables is INDEPENDENT VARIABLE. Independent variable is the variable that is changed or manipulated in the experiment.
In a controlled experiment, only one independent variable is used at a time i.e. ONLY one variable is changed or manipulated for each experiment. This is to ensure the validity of the experiment.
Answer:
i think it is the first one
Explanation: