Sentence improvement : through the proper channels vs through proper channels

Question

Which among the following sentence is best to choose considering it is asked in a MCQ pattern based exam ?

Your complaint must be made through the proper channels

A) through proper channel

B) through proper channels

C) with proper channels

D) no improvement

Given options should replace just the bold part of the sentence.

C is grammatically wrong. A is also wrong as it changes meaning here. (Changes channels to channel). I am confused between option B and D. Do we need use here the article the or not ?

Answer 1

The idiom is

through the proper channels

so D would be correct, it is fine as is.

Answer 2

The best choice here is D) no improvement.

Both through the proper channels and through proper channels (without a definite article) can be used, but in this case the definite article is better because the speaker presumably means some particular "proper channels". You might imagine the conversation in real life continuing like this:

Your complaint must be made through the proper channels. Start by submitting a work order request on our website, and if you aren't satisfied you can file an appeal with the Board of Overseers.

I suspect the definite article is much more common in the imperative for this reason, even though you can find many examples of the phrase without an article in other contexts.