Avector changes if
1. any of these
2. its direction changes.
3. its direction and magnitude both change.
4. its magnitude changes.
5. none of these

Vector is described as a quantity that have both direction and magnitude

A vector will change if : 
- It's direction and magnitude both change
- It's direction change
- It's magnitude change

So i guess the asnwer will be 1. any of these

Hope this helps