In a Recent Study Designed to Determine the Effectiveness of Antidepressant

In a recent study designed to determine the effectiveness of antidepressant medication,depressed patients were randomly assigned to take either an antidepressant medication or a placebo.Symptoms of depression were measured before and during treatment.Over the course of treatment,both groups reported decreased symptoms of depression.The investigators still concluded that antidepressants were clinically effective because:

A) those taking the antidepressants had larger reductions in symptoms.
B) taking a larger dose of an antidepressant produced larger reductions in symptoms than did a smaller dose or placebo.
C) the benefits of taking the placebo tended to be temporary.
D) the antidepressant medication was more effective than was a placebo for patients experiencing severe symptoms of depression.