These topics would be helpful when writing about sixteenth-century journeys to the New World. Shipbuilding was a significant element of these journeys, as the countries with better shipbuilding skills were the ones that dominated the oceans. Early discoveries are also significant to discuss, as they often led to increasing the exploration efforts. Finally, the study of famous explorers can help us understand many of the motivations behind exploration. Air travel and satellite technology, however, had not been invented at that point in history.
(Last sentence) Do you believe the story about the president (George Washington) who, as a boy, admitted to his father that he cut down the cherry tree?
Defend and challenge are pretty much the opposite of each other here. To defend an argument is to persuade others why the argument is sound. To challenge an argument means you are arguing against IT.
