一台显微镜有10×20×30×三个目镜，有5×15×两个物镜，这台显微镜最小放大倍数和最大放大倍数是（　　）

A．150倍、300倍

B．50倍、450倍

C．100倍、150倍

D．50倍、300倍

在以British and American English为主题的课堂前面列出以下四条名人语录，组织学生进行讨论。
(a) We have really everything in common with America nowadays except, of course, language.
(b) Within a century British and America English speakers will not be able to understand each other.
(c) America and English are two countries divided by a common language.
(d) It doesn’t make much of a difference whether a teacher speaks British or America English.
试对以上案例进行分析。