Thanks for the question! So this question is asking what the author thinks the US Constitution does with regard to the use of troops in a foreign conflict without a formal declaration of war. Well, take a look at the last sentence. Congressional involvement in decisions to use armed force is in accord with the intent and spirit of the Constitution. So that supports the involvement of the Congress. But the President also is commander in chief (see line 16). So both need to be involved in the decision, which supports (E), not (C). (C) is wrong because no one says Congress should have more authority than the President, just that Congress should have more authority than it does now.
Hope this helps! Feel free to ask any other questions that you might have.