The option that describes a step in designing a controlled experiment is identifying the independent (manipulated) and dependent (responding) variables (option D).
A controlled experiment is an experiment in which all the variable factors in an experimental group and a comparison control group are kept the same except for one variable factor in the experimental group that is changed or altered (independent variable).
An experiment is usually made up of an independent variable and a dependent variable.
However, in a controlled experiment, only one independent and dependent variable can be used, while all other variables are kept constant or controlled.
Therefore, the option that describes a step in designing a controlled experiment is identifying the independent (manipulated) and dependent (responding) variables.
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