The answer to your question would be that the word or group of words that is the complete subject is the following one: Benjamin Franklin.
The subject of a sentence is the person, object, place or idea that is doing or being something. You can identify the subject of the sentence if you can identify the verb by asking the following question: Who (verb) ?
Question: Who disagreed with the Second Continental Congress, which had selected the bald eagle to symbolize the United States?
Answer: Benjamin Franklin
