玉米穗期田间管理的中心任务是（）
A、保全苗
B、促根壮苗
C、促叶壮秆
D、保护叶片不早衰
参考答案：C
— Have you seen Tony recently?
— No, but I ______ dinner with him on Sunday. [ ]
A. would have
B. have had
C. have been having
D. am having
两列火车从相距399千米的两地同时相对开出，经过2.1小时两车相遇．甲车每小时行98千米，乙车每小时行多少千米？
