1. During the long spelling bee, the young contestant was indefatigable. A synonym for indefatigable is B. Inexhaustible.
2. The INVINCIBLE athlete won three gold medals - a synonym for invincible is unbeatable. Therefore, C. would be your answer.
3. Even though it was clear she did not understand the concepts, she DEMENTEDLY rambled about her failed math test - a synonym for dementedly is madly. Therefore, D. would be your answer.
4. The synonym for OSTENTATIOUS is loud and showy. Therefore, A and B could be correct answers.
5. The synonym for Oblivious is D. unaware. Therefore, D would be the correct choice.