she definitely wanted to be a physicist, or she _____  studied physics at the university

1. must have 2. would have

저는 둘다 되는거 같은데...더 맞는건 추측이니까 2번같은데 맞나요?

I ____ taken the train instead of this bus!

1. could have 2. couldn't have 3.must have

이건 전 3번같은데 3번은 ~했어야하는데로 해석되고

1은 나는 이 버스대신 기차 탈 수 있었어로 해석되는데

3번같은데 뭐가 맞나요?