Choose the correct item. Joshua ...... incredibly well today.

The correct answer is "is behaving". The sentence is in the present continuous tense which requires the auxiliary verb "is" and the present participle of the main verb. Правильный ответ: "is behaving". Предложение построено во времени Present Continuous, которое требует вспомогательного глагола "is" и причастия настоящего времени основного глагола.