The answer is: C
In option A the writer talks about an assertion and in option B he expresses his disagreement with this assertion. <em>In option C, the writer clearly supports the claim that the American colonies could thrive independently from Britain.</em> Option D only extends the general idea.
The FIRST ONE and the THIRD ONE, hope this helped.
You need another comma after the word "think" because it's a parenthetical expression and is set off from the sentence.
1. having my favorite show canceled is minor
2. getting a haircut is major
3. gaining a new best friend is minor
4. repainting my room is major
5. going to a new school is major
6. moving far away is major