Both 1) and 3) are wrong, and I'm absolutely certain about this. (provided you understood the questions correctly) The correct answers are: 1: 4 2: 2 3: 1 1) The noun with "거든" attached cannot act as the subject in the following part. 2) The ~고서 conjunction doesn't "share" the object. (동화책 in this case) 동화책을 사고서 집에 갈 거예요. I'm going to buy a fairy tale book and then go home. The sentence above is ok because both parts don't share the object. 3) ~만큼 means "as much as", and it's not compatible with duration. However, if you are looking for the equivalent one, the correct answer is 3.

Hi. I am Korean. And I want to say that you are really great study korean. I shocked saw your question, because the problems is not easy even korean. But, if you understand question, you can solve them. 1. A:저 수학 문제는 정말 어려운데요. : The math problem is really difficult. B:맞아요._____________________. : You are right. ... (1)수학을 전공한 사람이면 풀 수 있을 것 같아요. : If someone who major Mathematics, then solve it. (2)수학을 전공한 사람이라도 풀 수 없을 것 같아요. : Even someone who major Mathematics, can't solve it. (3)수학을 전공한 사람이어야 풀 수 있을 것 같아요. : Only one who major Mathematics, can solve it. (4)수학을 전공한 사람이거든 풀 수 있을 것 같아요. : Who major Mathematics, (then do something... ) > ex) 합격을 하거든 술을 사라. 실패했거든 새로 시작해라. 힘들거든 쉬어라. Choose one from the above which is inappropriate to fill in the blank. Answer:(3) : No, answer is (4) 2. A:마크 씨, 동화책을 사려고 해요? : Mark, Are you going to buy fairy tale book? B:네,_____________________ 조카에게 선물로 줄 거에요. : Yes, ... It's present for nephew. (1)동화책을 사서 : After buy book, (2)동화책을 사고서 : 사고(o), 사고서(x) (3)동화책을 사다가 : After buy book and keep it, (4)동화책을 사 가지고 : After buy book and keep it, Choose one from the above which is inappropriate to fill in the blank. Answer:(2) > right. 3. 초등학교 때 친구를 "10년 만에 다시 만났어요". : meet friend again after 10 years. (1)친구를 10년만큼 만났어요 : 10년만큼(x), 그리워할 만큼(o) (2)친구를 10년 동안 만났어요: meet friend during 10 years. > meaning is opposite (3)친구를 10년이 지나서 만났어요 : passed 10 years, meet friend again. (4)친구를 10년 전만 해도 만났어요: before 10 years, meet friend. Choose one from the above which can not replace the part quoted Answer:(3) > right. Shouldn't (1) and (2) be 친구를 10년만큼 "못" 만났어요 and 친구를 10년 동안 "못" 만났어요?

The answee of No.3 is definately 3 but No1 and 2 seem to be very weired. Im 100% korean but i cannot understand why they put answers as 3 and 2. I think its no needed to understand their answers for question no 1 and 2.