Addition of a progestin for 10-12 days each month to estrogen replacement therapy in menopausal women is recommended because the progestin

A) Blocks the increased risk of myocardial infarction due to estrogen B) Blocks the increased risk of endometrial carcinoma due to estrogen C) Reverses vulval atrophy occurring in postmenopausal women D) Enhances the metabolic benefits of estrogen treatment