B. Third parties can often times gather enough votes to swing some votes in various elections.
That would be a literacy test.
A volcanic eruption or extreme flooding.
The correct answer here is (4) Mongols.
The Mongols were a nomadic people who travelled on horseback and were very proficient archers. They were said to be able to shoot a target from full horseback speed with their bows.
They were led by Genghis Khan and conquered a good portion of Asia and also entered parts of Europe. Their empire was one of the biggest ones to date.