Is there a bank in the town?---Yes,but it's about_____walk.I

Is there a bank in the town?---Yes,but it's about_____walk.I think you'd better go there by taxi.
Is there a bank in the town?
Yes,but it's about_____walk.I think you'd better go there by taxi.
A: fifty minutes
B: fifty minutes'
C: fifty-minute's
D: fifty-minute