Read the sentence. You can delight any toddler by blowing bubbles on a sunny afternoon. How is the phrase "blowing bubbles" used
in the sentence? It is a gerund phrase used as the object of the preposition by. It is an infinitive phrase used as an adverb modifying the phrase "on a sunny afternoon." It is a participle phrase modifying the word delight. It is a gerund phrase that is the subject of the sentence.
I don't know which book this is, (either the Adventures of Huckleberry Finn or the Adventures of Tom Sawyer), but I believe the answer is A. The latter book occurred before the former book, and the former book was about helping Jim escape.
