Do you think the League of Nations could have prevented the outbreak of the Second World War if the United States had joined? Why or why not

No, it was designed to prevent another WW1. It was premised on the assumption that IF only the heads of state and the foreign ministers spoke directly, then behaved as gentlemen would, then all future wars would be avoided.

Explanation:

If the US has joined, not only would it not have stopped World War II, but it would have involved us sooner. Since we were isolationists, that's quite a different version of history. It is highly unlikely that U.S. participation in the League would have prevented or even postponed World War I.

b.

jim crow laws were enacted in northern states.

this means that germany had to pay the allied countries. reparations are/is essentially payment for something that they have done wrong, so after ww1, germany was forced to pay reparations so they could replenish the allied countries resources' that they had lost during the war.