The correct answer is D. He knows that it was written to support political candidates.
Explanation:
Yes, the Declaration of Independence provided America and its people with independence from Britain, but Roosevelt clearly understands that one additional purpose was to give American government and its political candidates more power, while giving its people some rights. The point is about power and support - not for the people per se, but for politicians and governments.
Because ‘Sarah and her sisters has gone’ doesn’t sound right, ‘Sarah and her sisters has been’ also sounds wrong and ‘Sarah and her sisters have been’ doesn’t really make sense