B. Peace
All of the options have something to do with John Locke's political theory. A government gets its authority and legitimacy from the consent of the people (the governed), in Locke's view. This will lead to the greatest amount of prosperity for a country.
But as far as the social contract is concerned, in Locke's theory, human beings enter into a social contract and form a government over themselves as a society in order to promote peace and resolve disagreements. Locke suggested that people in a "state of nature" could live relatively peacefully side by side ... but inevitably disputes would occur. When there were disputes over borders, property, etc, the most peaceful way to resolve such disputes is to have established government officials and procedures to manage the situation.
My usual way of teaching Locke's social contract theory is this. A bunch of folks could have a pretty good pickup game of basketball on the playground ... but there are bound to be disputes. One person claims he was fouled; the other player denies it and says there was no foul. The most peaceful and successful way to have the best sort of basketball game is to agree (in a social contract) to have a referee officiate the game. In Locke's view of government, we empower governments to serve as the "referees" of our society for a more peaceable order to be achieved.