Answer:
Option C: He refutes the idea that America depends on Britain, using the opinion that America's trade has a secure future.
Explanation:
Thomas Paine refutes the argument stated in the beginning of the passage. He refutes it not on a single basis but on two basis.
First he refutes it by stating, "Nothing can be more fallacious than this kind of argument." And, next he says, "But even this is admitting more than is true, for I answer roundly, that America would have flourished as much, and probably much more...".
So, what Thomas really wants to say is that America would still have flourished even without British or any other European countries because America had enriched herself by commerce.
Options A and B are incorrect because this is the argument he is trying to refute.
No such thing as in option D is presented in this passage.