教学要按照学科的逻辑系统和学生认识发展的顺序进行，这是教学的 （ ）原则。
参考答案：循序渐进
— Pity you missed the wonderful opening ceremony of our sports meeting!
— I _______it, but I was absorbed in preparing the mid-term paper for English.[ ]
A. watched
B. had watched
C. would have watched
D. would watch
城市轨道为了避免事故，需要有安全可靠、功能互补的各类安全保障系统。其中（）代表环境与设备监控系统。
A.ATC
B.FAS
C.ISCS
D.BAS
