In this mountainous area; it often takes the students two hours to go to their boarding school

1. In this mountainous area, it often takes the students two hours to go to their boarding school.
A. How much does it take the students in this mountainous area to go to their boarding school?
B. How long does it take the students in this mountainous area to go to their boarding school?
C. How much do the students in this mountainous area go to their boarding school?
D. How long do the students in this mountainous area go to their boarding school?
2. Tet is the most important festival in Vietnam.
A. Which is the most important festival in Vietnam?
B. When is the most important festival in Vietnam?
C. Where is the most important festival in Vietnam?
D. Why is the most important festival in Vietnam?
3. Muong's men often wear round-neck shirts.
A. What does Muong's men often wear?
B. What do Muong's men often wear?
C. Which does Muong's men often wear?
D. Which do Muong's men often wear?
4. How long have you been an ethnologist?
A. When were you an ethnologist?
B. When have you been an ethnologist?
C. When did you become an ethnologist?
D. When are you an ethnologist?
5. Who does this beautiful watch belong to?
A. Whose is this beautiful watch?
B. Whose does this beautiful watch?
C. Which is this watch?
D. Which is the owner of this watch?