18. Although it claims to delve into political issues, television can be superficial such as when each of the three major networks broadcast exactly the same statement from a political candidate.

    A) superficial such as when each of the three major networks

   B) superficial, as can sometimes occur if all of the three major networks

   C) superficial if the three major networks all

   D) superficial whenever each of the three major networks

   E) superfical, as when the three major networks each

问题：

as when什么意思？开头的it指什么？谢谢大家指教！

 as when 意思是就像……的时候。举例的意思。

it 指的是television

 it claim to宣称，标榜的意思啊

尽管电视媒体一直标榜深入探讨政治问题，.....

delve into....不常见的短语，我也不知道什么意思。不过后面有superficial，可以通过although的让步语气推断这个短语的意思恰好与superficial相反。

if引导条件从句，means只在这种情况（三电视台。。。），电视才superficial，而原文提到三电视台。。。，只是一个举例还有其他的很多情况。

此题经典的是each
each of+Vs，名复+each+v

delve into研究钻研=investigate