15. History New words: pirate (n): a person who steals something, traditionally from ships on the sea海盗 bet (v): to feel confident about an idea sword (n): a weapon with a long sharp剑 cannon (n): a large mounted gun that shoots heavy metal balls大炮 rifle (n): a gun with a long barrel, which requires two hands to hold and shoot步枪 What aspect of history does the professor mainly discuss? A. Criminals. B. Methods of travel. C. Wars. D. Novels.