The Term Transsexual, as Used in the Study of Sex

The term transsexual, as used in the study of sex and gender, refers to which of the following situations?

A) an intersexed individual who lives part-time as a male and part-time as a female
B) a male person who dresses as a female for entertainment
C) an individual who lives as the opposite gender full-time because it is congruent with their gender identity
D) an individual who secretly wears the clothing of, and pretends to be, of the opposite sex because it reduces their anxiety