根据以下内容回答下面的题目，Flying on a plane Can cost a lot of money．Now is a good time to buy plane tickets at a low price．Many airlines(航空公司)are selling 41 tickets． A woman from a news station says that there are good 42 now．But she also says that you 43 be careful．You need to be sure 44 you really want these tickets before buying them．If changes need 45 it will cost a lot of money．You also need to 46 your tickets before the middle of December． The 47 will not lose any money 48 selling these cheap tickets．They believe that many people will buy 49 ．they will sell 50 tickets now because they cost less money．

A. made
B. to make
C. to be made