以下电报里C/B的意思是（ ） ZCZC 5HK0041 260552 GG ZGGGUDXX 260552 ZBBBCKXX ATTN:GDO/D CSN OCT C/B FLIGHT PLAN AS FLW: AIRCRAFT TYPE:A320 DATE AND SKED:PEK TIME 1.CSN3310 ZSPD0415 0545ZHCC ON 07/14/21/28OCT2015 FLIGHT ROUTE:AS SKED FLIGHT LEVEL:AS SKED PLS ENSURE/WLK/87786586
A.客运加班
B.货运包机
C.调机
D.训练
正确答案是A