연구사 is totally wrong. It should be 연구원
"연구원" 76 200 000
"연구자" 15 700 000
"연구사" 802 000
Though I'd say these are people of increasing status: underling researcher, head researcher, top-class researcher. I wish I knew more about Korean and its society . . .
研究士는 檢查할 것이라고 했어요.
Can I say 연구원은 검사를 할 것이라고 했어요?
That's what I put, and they marked as wrong, though 검사를 하다 and 검사하다 are the same, so I'd say yes, it should be correct. 연구원 is the more common term for "researcher" so idk why they decided to add 연구사.