It would be a. "We the people of the United States ... do ordain and establish this Constitution for the United States of America."
We can rule out c immediately, because it has dependent clauses standing on its own. B. can also be ruled out, because the clause in-between the hyphen does not read correctly. A. is correct grammatically, but D. is also grammatically correct and it explains it in a quick and understandable way.
Well! You've got a strong topic, now you just need to get your template down. It's an argumentative essay, so you're going to want an attention-grabbing introduction with your thesis statement. You're going to want body paragraphs that explain both sides of the debate, and then try to convince the reader that your side (the federal gov side) is the best position to take. Wrap it up with a conclusion and voila!
One of your points may be that federal power covers all 50 states, meanwhile state gun laws only govern the individual state. Strict gun laws in Illinois don't matter if it's only a two hour drive to Indiana where they have much looser laws.
Can I have a bit of clarification? I don't completely understand.
Very important. if you didn't know then you couldn't properly imagine the scene of the story