밑줄 친 부분 중 어법상 틀린 부분 찾는 문제입니다.

columbus became the first man to navigate an atlantic crossing from the old world to the new by doing what ①none before him had dared attempt, setting course directly out into the ocean’s vast uncharted waters rather than hugging the shore. all previous, failed efforts to cross the atlantic had been made by sailors who ②clung to westerly winds along the european coast in order to ensure a means of return. not so columbus ③what, according to oxford university historian felipe fernandez-armesto, “was the first to succeed precisely because he had the courage to sail with the wind at his back.” turning his back also on the safety of the coastline that previous explorers were ④reluctant to leave. columbus sailed perpendicular to the shoreline, straight away from civilization, even though he did not know what ⑤lay ahead.