A study is designed to evaluate the feasibility of acupuncture in children with chronic headaches. Sixty children with chronic headaches are recruited for the study. In addition to their usual therapy, all children are treated with acupuncture three times a week for 2 months. Which of the following best describes this study design?

(A) Case-control

(B) Case series

(C) Crossover

(D) Cross-sectional

(E) Historical cohort

(F) Randomized clinical trial