Which Statement Is Accurate

Which statement is accurate?

A) Premenstrual dysphoric disorder (PMDD) is a severe form of premenstrual syndrome (PMS) and more common in younger women.
B) Secondary dysmenorrhea is more intense and medically significant than primary dysmenorrhea.
C) Premenstrual syndrome is a complex but clearly understood condition that may include many symptoms.
D) The causes of PMS have been well established.