commas go where the sentence changes the subject but is still a sentence
1. Assuming that the underlined words are 'Carl Sandburg,' the correct answer is A. simple subject. Although you may be led to believe this is a complete subject (because it consists of more than one word), in fact, it is not. Carl Sandburg is the name and the surname of one person, which is why it is considered to be a simple, rather than a complete subject.
2. Assuming that the underlined words are '<span>served as a soldier during the Spanish-American War,' the correct answer is D. complete predicate. As you can see, these words include the simple verb served, as well as all other words which modify, or describe that verb. This is why this is complete, rather than a simple predicate. Simple predicate would be only the word served.
3. Assuming that the underlined words are 'would influence,' the correct answer is B. simple predicate. Similarly to the first sentence, you may be led to believe this is complete because there are more than one word in the phrase. However, the verb phrase would influence is considered to be one entity given that it is only a particular tense of that verb. Even if it said 'had been influencing' instead of 'would influence,' it would still be a simple predicate.</span>
A text-based answer on an essay test about literature will almost always include D. text quotations.
Hope this helps ;)
