It's a very tricky question, but probably not a very good one because there are two different versions of the conjunction "다가" A) present B) past C) past D) present A & D (present): "다가" translates to "while [process] an event occurs that terminates/interrupts the process" A: while [writing down], a hand injury occurs, and the writing process most probably got terminated D: while [eating out], I had to go home for an unknown reason, thus terminating the eating process C (past): "다가" translates to "did [1], then [2] happened as an (mostly undesired/unpleasant) result" As you can see, [1] and [2] have to be in a direct relation in this case. And B) doesn't qualify because "handing over the filled form" isn't directly related to "meeting a friend" Below are VALID examples: present: 은행에서 청구서를 내다가 친구를 만났어요 과속하다가 경찰에 잡혔어요: while driving too fast I got stopped by the police past: 은행에 청구서를 냈다가 거절당했어요: applied for something, but rejected 과속했다가 경찰에 잡혔어요: I drove too fast, and got caught by the police 이탈리아에 여행갔다가 바가지만 썼어요: I traveled to Italy, and only got ripped off 면접 갔다가 시간만 낭비했어요: I went to a job interview, and just wasted time

b) is unnatural because there is no relation between the first action(청구서를 내다) and the second action(친구를 만나다). -다가 is a verb connector which connects two verbs. It means the first action(verb1) has finished yet, but the action changes to the second action(verb2). For example, 밥을 먹다가 나갔어요. In the middle of eating, he went out. (the action of eating hasn’t finished) 잠을 자다가 깼어요. In the middle of sleeping, I woke up. (the action of sleeping hasn’t finished) 청소하다가 다쳤어요. In the middle of cleaning, I hurt myself. (the action of cleaning hasn’t finished) 발표를 하다가 잊어버렸어요. In the middle of presentation, I forgot. (the presentation hasn’t finished) 왜 말을 하다가 멈춰요? Why do you stop in the middle of speaking? 편지를 쓰다가 친구 생각이 났어요. In the middle of writing a letter, I thought about my friend. 한국어를 공부하다가 너무 어려워서 포기했어요. In the middle of studying Korean, I gave up because it was too difficult. 시험을 보다가 잠이 들었어요. In the middle of the test, I feel asleep. (Oh, no!!!!!!) 학교에 가다가 친구를 만났어요. On the way to school, I met my friend. 집에 가다가 슈퍼에 들렀어요. On the way home, I stopped by a supermarket.

Yes. the Answer is B. Because we have to find "~다가 not be used in place of the blank" Usually(in this case), "~다가" means: 1) to do + verb ~ing and then now to do another thing 2) to do sth and then to do opposite sth 3) to do sth(cause) so now to get sth(result) a) 제가 공책에 글을 빨리 쓰_____ 손을 다쳤어요 => 3) b) 은행에서 청구서를 냈____ 친구를 만났어요 c) 그 학생이 열심히 공부를 했_____ 시험을 포기했어요 => 2) d) 외식을 하____ 집에 돌아왔어요 => 1) if you want to make b) has the meaning of 1) 은행에서 청구서를 내____ 친구를 만났어요 hope it helps

I think a), because the most natural.