The correct answer is C. To avoid harmful exposure to the sun's direct rays
Step-by-step explanation:
In the English language, an infinitive is the basic form of verbs that is composed by the preposition "to" and the verb without any modification for example to avoid, to play or to go. Additionally, an infinitive phrase is a set of words containing an infinitive and other words that express or add information about the action of the infinitive. Most infinitive phrases work as nouns in sentences but can also work as adjectives or adverbs. Considering the previous ideas in the case of the sentence "It is important to avoid harmful exposure to the sun’s direct rays" the infinitive is "to avoid" as this is the part of the sentence composed by the preposition "to" and the verb avoid. This means the infinitive phrase, in this case, is C "To avoid harmful exposure to the sun's direct rays" as this is the section of the sentence that contains the infinitive along with other words that explain what should be avoided.