Which sentence is correct?
Options:We always go to the mountains in the fall; they are at their prettiest at that time of year.
,We always go to the mountains in the fall they are at their prettiest at that time of year.
,We always go to the mountains in the fall, they are at their prettiest at that time of year.
,We always go to the mountains, in the fall; they are at their prettiest at that time of year.