2012학년도 3월 고2 전국연합학력평가에 나왔던 지문인데요...(26번)
in some cases two species are do dependent upon each other that if one becomes extinct, the other will as well.
this nearly happened with tress that relied on the now- extinct dodo birds.
라는 부분이 있는데요... 거기서 relied on을 had relied on 으로 바꿔쓸 수 도 있나요?