다음 글의 밑줄 친 부분 중 어법상 옳지 않은 것은?After lots… | [법원직 9급 영어] 18년 1회차 기출문제 상세 페이지

다음 글의 밑줄 친 부분 중 어법상 옳지 않은 것은?
After lots of trial and error, Richard finally created a system of flashing LED lights, ①powered by an old car battery that was charged by a solar panel. Richard set the lights up along the fence. At night, the lights could be seen from outside the stable and took turns flashing, ②which appeared as if people were moving around with torches. Never again ③lions crossed Richard's fence. Richard called his system Lion Lights. This simple and practical device did no harm to lions, so human beings, cattle, and lions were finally able to make peace with ④one another.

①

②

③

④