어휘 유추고2 · 2019년 3월 · 35번1/6

S1 문장의 [______]에 들어갈 단어는?

난이도 필수 · 힌트를 덜 열수록 높은 점수 (현재 5점)
When we were infants, we were tuned in to the [______] from our body that told us when to eat and when to stop.