Sickle-cell disease is a painful disorder of the red blood cells that in the United States affects mostly African Americans. To investigate whether the drug hydroxyurea can reduce the pain associated with sickle-cell disease, a study by the National Institutes of Health gave the drug to 150 sickle-cell sufferers and a placebo to another 150 sufferers. The researchers then counted the number of episodes of pain reported by each subject. What is the response variable in this study

The response variable is; reduction in the pain associated with sickle-cell disease.

Explanation:

Note, a response variable (dependent variable) simply refers to resulting effect (either significant or insignificant effect) of the independent variable on the subjects of the experiment.

In other words, the effect of the drug hydroxyurea after the experiment would show whether it leads to or not lead to a reduction in the pain associated with sickle-cell disease.

correct answer:

a + bi

i believe the answer is c.