33.坊間常聽到的藥物威而剛(Viagra),主要是用來治療何種性功能障礙症?(A)勃起障礙(erectile disorder)(B)男性性慾低下障礙症(male hypoactive sexual desire disorder)(C)早發性射精(premature ejaculation)(D)延遲性射精(delayed ejaculation)