<h2>Right answer: fácilmente
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Firtsly, is important to explain that an <u>adverb</u> is a part of the sentence that complements a verb, an adjective, other adverbs and even sentences.
Adverbs express circumstances, such as mode, place, time, quantity, affirmation, doubt; answering questions such as: when?, where?, how?, in what way?, among others.
In other words:
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The main function of adverbs is to act as modifiers or complements of a verb or verbal phrase
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Now, in Spanish there are several types of adverbs, but in this specific case we are talking about the adverb of manner.
The <u>adverb of manner</u> can be formed by placing the suffix -mente at the end of some adjectives.
As it is the case of the <u>adjective</u> fácil (easy) that changes to an <u>adverb of manner</u> as fácilmente (easily).