Hello there
Action verbs, also called dynamic verbs, express an action.
Options A and B would not work because they are using to be verb, wich is a linking verb. its main fonction is link the subject with the adjective (happy and nervous)
Options D Y C would work, but option D is using a verb another possible linking verb.
Therefore, correct answer is C. THINK a totally action verb, it represents an effort.
Hope this helps
