在空格内填入适当的单词（首字母已给
1.The b__1__time to buy is about two or three months before departure ,according to studies of airline-fare trends.
2.Any earlier,you may end up plating h__2__of dollars more for the same seat as someone who books later.
3."Fares start out real high and then d__3__
4.Choosing w__4__to buy a ticket is one of the most difficult decis ions for travelers.
5.International sales are s__5__,not weekly