On a second level, public relations becomes the vehicle through which management reaches the public with assorted messages to accomplish organizational goals.

In this sentence, what does "which" mean or refer to ? What if this sentence lacks "which" ?
Please explain this from a gramatical point of view.

Посмотреть перевод

It's because the sentence is structured with "public relations" at the beginning, probably because this is the main subject. Consider this sentence:

Management reaches the public [with assorted messages to accomplish organisational goals] through the vehicle of public relations.
- There is no "which".

However, since we are putting public relations first, we need to refer back to it to explain its relation to the following part of the sentence, hence - it is the vehicle through which management...

It doesn't make sense without "which".

https://dictionary.cambridge.org/dictionary/eng...
which pronoun (USED TO REFER)
A2
used as the subject or object of a verb to show what thing or things you are referring to, or to add information about the thing just mentioned. It is usually used for things, not people: