Answer:
2). The librarian’s suggestion—to read the newest magazine article about large lizards—was a good one!
Step-by-step explanation:
Infinitives are demonstrated as the base form of verbs preceded by 'to.' The phrases consisting of infinitive plus other objects or modifiers function as nouns, adjectives, or adverbs in the sentence.
As per the question, the second sentence involves the infinitive 'to read' that functions as an adverb in it as it modifies the verb 'was' and adjective 'good' by adding details about them. The other sentences either employ infinitives as adjectives. Thus, option 2 is the correct answer.