"I chose to run for the President at this moment in history because I believe deeply that we cannot solve the challenges of our time unless we solve them together--unless we perfect our union by understanding that we may have different stories, but we hold common hopes; that we may not look the same and we may not have come from the same place, but we all want to move in the same direction." The rhetorical device is .
选项：

A:metonymy
B:antithesis
C:parallelism
D:metaphor