문제 내용: 글의 흐름상 가장 어색한 문장은?
선택지 1: ① In the early 1900s, few cancer patients had any hope of long-term survival.
선택지 2: ② But because of advances in medical technology, progress has been made so that currently four in ten cancer patients survive.
선택지 3: ③ It has been proven that smoking is a direct cause of lung cancer.
선택지 4: ④ However, the battle has not yet been won. Although cures for some forms of cancer have been discovered, other forms of cancer are still increasing.