The correct answer is B) mobilizing voters, helping raise money, and creating a more permanent party presence in the states.
In order to build the party as an organization, some activities that a president might engage in as the leader of his or her party are "mobilizing voters, helping raise money, and creating a more permanent party presence in the states."
The President of the United States is also the best and most important representative of his political party. We could say that is the true leader of the party because all his actions and decision directly impact his public image and the public image of the political party.
That is why he and teh party have to work hand in hand, creation the kind of actions and communication policy that conveys the citizens the right messages to influence public opinion.