北师大版高中英语选修7 Unit19:

 What this means is that they make sure there is an adequate amount of input in English conveyed to the students through various mediums.中medium的复数对不对？

柯林斯词典：

medium表示“（表现）方式；（交流）手段”或“媒介；介质；媒介物”时复数形式为mediums或media。若表示“巫师；灵媒”时复数形式为mediums。例如：

In Sierra Leone, English is used as the medium of instruction for all primary education...

在塞拉利昂，基础教育阶段全部用英语授课。（柯林斯词典）

Blood is the medium in which oxygen is carried to all parts of the body.

血液是将氧气输送到人体各个部位的媒介。（柯林斯词典）

A good deal of adult education is accomplished by the mass media.

成人教育的相当一部分是由大众传媒媒介完成的。（英汉词典）

A conductor that passes current between two different conducting mediums.

在两个不同的导电媒体之间传递电流的一种导体。（爱词霸英汉例句精华）

Mediums claim to receive messages from the spirit world. 
通灵的人声称收到来自阴间的信息。（英语常用词例句库）