Step 1: Understanding Female Athlete Triad.
The Female Athlete Triad is a medical condition often seen in female athletes, characterized by three interrelated conditions: \textit{Amenorrhea} (lack of menstrual periods), \textit{Oligomenorrhea} (infrequent menstrual periods), and \textit{Osteoporosis} (bone density loss). These conditions can result from low energy availability due to inadequate nutrition and excessive exercise.
Step 2: Comparison with other options.
- (A) Amenorrhea: Correct. Amenorrhea is part of the Female Athlete Triad, as it refers to the absence of menstrual periods.
- (B) Oligomenorrhea: Correct. Oligomenorrhea refers to infrequent menstrual periods, which is also part of the triad.
- (C) Osteoporosis: Correct. Osteoporosis, or reduced bone density, is the third condition in the Female Athlete Triad.
- (D) Bulimia Nervosa: Incorrect. Bulimia Nervosa is an eating disorder characterized by binge eating followed by purging. It is not part of the Female Athlete Triad.
Step 3: Conclusion.
Therefore,
(D) Bulimia Nervosa is the correct answer as it is not part of the Female Athlete Triad.
Final Answer:} Bulimia Nervosa.