Final answer:
Gerunds and infinitives can be used as nouns in a sentence. Gerunds are verbs ending in -ing which act as nouns, while infinitives are base verbs often preceded by 'to' and can fulfill noun roles.
Step-by-step explanation:
The sentence elements that can be used as nouns include B) Gerunds and C) Infinitives.
Gerunds are -ing verbs that function as nouns. They can perform the role of a subject, direct object, subject complement, and object of a preposition. For example, in the sentence 'Swimming is fun,' 'swimming' is a gerund functioning as the subject. Gerund phrases give us more information about the gerund by adding objects or modifiers, such as in 'Swimming in the ocean can be risky.' Here, 'swimming in the ocean' is the gerund phrase acting as a subject.
Infinitives are the base form of a verb that is often preceded by the word to. Infinitives can act as nouns, adjectives, or adverbs. As nouns, they can take the role of a subject or an object in a sentence. For instance, 'To read brings joy to my life,' where 'To read' is the infinitive acting as the subject.