Researchers studied the herb black cohosh as a treatment for hot flashes caused by menopause. They randomly assigned women aged to who reported at least two hot flashes a day to one of five​ groups: black​ cohosh, a multiherb supplement with black​ cohosh, the multiherb supplement plus advice to consume more soy​ foods, estrogen replacement​ therapy, or a placebo. After a​ year, only the women given estrogen replacement therapy had symptoms different from those of the placebo group. Complete parts​ a) through​ d) below.