Mike will go abroad tomorrow. I am going to _____ at the airport.
A:sent him off
B:saw him off
C:see off
D:see him off
实验室备有甲、乙、丙三个凸透镜,三个实验小组分别用这三个凸透镜探究凸透镜成像规律,实验时,当蜡烛到透镜的距离都为12cm时,甲、乙、丙三透镜分别成缩小的实像、放大的虚像、放大的实像,则这三个透镜的焦距f甲、f乙、f丙的大小关系为( )
南水北调工程是世界上规模最大的调水工程,读图回答:
工业集聚可以( )①提高生产成本②扩大总体生产能力③提高环境质量④提高经济效益
— My computer has gone wrong. It needs _______ soon.— Why not have David _______ it? Nobody can if he can't.