An means "Is it possible?"

It means that those who are crowned kings, dukes, generals, and prime ministers, are they destined by God at birth?

This is a rhetorical question. Chen Sheng and Wu Guang said this because they did not believe that people's fate was destined by God. They had the courage to rise up against them and called on the people at that time to rise up against Qin's tyranny.

In fact, the deeper meaning is that they can change their destiny through resistance, and they can also be granted the title of marquis and prime minister.