<span>struggling to survive through seemingly insurmountable odds.</span>
The answer is D. A verb that starts with "to" is in an infinitive verb form. It should be noted that a verb in this form does not function as a verb instead it functions as another part of speech. Infinitives can function as adverbs, adjectives or as nouns.
Thomas is a guy that only wants facts and only teaches facts
I believe that both are complete sentences.