That would be D. Lake Titicaca
The South had seceeded from the Union to form the Confederacy. They considered themselves an independent nation, and, therefore, did not follow the laws and amendments passed by the Union. In 1965, however, the Union won the war, thus ending the existence of the Confederacy.
I believe D is the correct answer. If Japan (or any country) were to be hit with the largest natural disaster in recent history, it would most likely sway people away from migrating into the country.