One of the Best Controlled Studies Concerning the Results of Stuttering

One of the best controlled studies concerning the results of stuttering therapy for school-aged children who stutter and conducted by Craig, et al. (1996) was discussed in your textbook. It compared three methods: intensive smooth speech, intensive electromyography (EMG) , and home-based smooth speech. A control group of no therapy was also employed. The investigators found that:

A) by the end of the therapy program all treatment groups improved by approximately 20% in terms of reduction in the frequency of stuttering
B) by the end of the therapy program all treatment groups improved by approximately 50% in terms of reduction in the frequency of stuttering
C) by the end of the therapy program all treatment groups improved by 85% to 90% in terms of reduction in the frequency of stuttering
D) the control group also improved by about 25%
E) none of the above is a correct description of the findings.