【单选题】一个15cm宽的光栅,每毫米内有1200个衍射单元,在可见光波段的中部(波长约为550nm)此光栅能分辨的最小波长差为多少?
【单选题】( )服务包括产品安装和使用说明、提供教育培训、客户跟踪、客户管理。
【单选题】The best grouping of teaching when the students are given the task to design a poster for a school event is _____.
【单选题】( )服务包括产品安装和使用说明、提供教育培训、客户跟踪、客户管理。
【简答题】Suppose you are the organiser of Campus Singer Contest.Design a poster for it .The posters in Practical Reading may help you.
【单选题】When stating problems, we can make a _____ with those from last year.