He wanted to help design the peace settlement ( treaty of Versailles )
Explanation:
In order to design any kind of peace treaty or settlement there has to be a kind of conflict /war which will give room to the designing/drafting of a peace settlement.
Woodrow Wilson was the president of the united states of America and led them to the world war 1. after the world war Wilson crafted the treaty of Versailles fourteen points which was one of his ideas and reason why he asked congress to declare war and be involved in the world war 1.
the last point in his fourteen point gave birth to the "league of nations" which helped to ensure world peace by protecting each other.
The best explanation why the area between Spain and Gaul was not part of the Roman empire until that later period was a culmination from both undesireability and difficulty in accessing this region due to its mountaineous nature. So I would wager the answer being both C and D - undesireability and difficulty in access.
