A: What hiking trail would you recommend?

B: The one _________ the ridge to the summit has stunning views.

(a) following

(c) followed

-> 왜 a가 답인지 모르겠어요.. 

A: Do potatoes go bad quickly?

B: _________ in a cool, dark place, they should be fine for weeks.

(a) Kept

(d) To be kept

-> 분사랑 to 부정사가 함께 나올때 어떻게 구분 하나요?ㅠ