How many variables should you change in a controlled experiment? one two four as many as possible

Controlled experiments only have one variable to ensure accuracy. If there is more than one variable, it will be difficult to draw precise conclusions.

the answer is 1. photosynthesis. glad to

the relative standard reduction potential of the half-cell in which reduction occurs; more positive than the other half-cell. reduction is a chemical process in which electrons are added to an atom or an ion; it always occurs accompanied by oxidation of the reducing agent.