Explanation:
Infinitive phrases include infinitives. ... Examples include, “to walk,” “to read,” or “to eat.” Infinitives can act as nouns, adjectives, or adverbs. As a noun, they might act as the subject of the sentence. For example, “To travel is the only thing on her mind.” As an adjective, they'll modify a noun.
b. Jack
c. animals
d. he
Dr. Smythe believes that in order to fully understand complex processes, such as taste, it is necessary to understand the purpose that taste plays in survival