题目

 If you are worried that the tickets will sell out, you can buy a ticket         .    A. in a row           B. in advance         C. on time           D. time after time 答案：B在( )里填上合适的数。6-3=( ) 6-4=（ ） 6-5=（ ）7-5 =( ) 7-3=（ ） 6-0=（ ）