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.

scientists have discovered that hiv does not cause aids by the virus's direct effect on the host's immune cells, but rather through the cells' lethal influence on one another. researchers from the gladstone institutes have revealed that hiv does not cause aids by the virus's

is this a question? wassup