Answer:
The correct answer is: nerviosamente.
Explanation:
There is a very simple way of making adverbs out of adjectives in Spanish. Those are mostly adverbs of manner (nerviosamente, tranquilamente, rápidamente, etc. - HOW?). We create them by adding a suffix <em>-mente </em>to the adjective.
alegre + mente = alegremente (happily)
triste + mente = tristemente (sadly)
We always take the singular form of the adjective (<em>alegre</em> and not <em>alegres</em>). If the adjective ends in <em>-o</em>, as in our case (nervios-o), we will always take the feminine form, ending in <em>-a.</em>
adjective: <em>nervioso</em>
adverb: <em>nerviosa + mente = </em><em>nerviosamente </em>
