An inactive substance or condition that has the appearance of the independent variable and that may cause participants in an experiment to improve or change behavior due to their belief is called​

A) ​a nocebo.
B) ​a placebo.
C) ​a dependent variable.
D) ​an experimental design.

The best choice is B - a placebo. A placebo is an inactive substance or condition that is given to participants in an experiment to control for the effects of expectation and suggestion. It has the appearance of the independent variable but does not actually contain any active ingredients or produce any therapeutic effect. Placebos may cause participants to improve or change behavior due to their belief in the treatment, which is known as the placebo effect. A nocebo, on the other hand, is an inactive substance or condition that has a negative effect on participants due to their negative beliefs or expectations. The dependent variable is the variable that is measured in an experiment, and an experimental design is the plan for conducting an experiment.