Use of different discourses?

[working on it]

The examiner recommends in the essay question paper that while one writes essay one should use different discourses. He quotes some example.

"The essay should be comprehensive. The essay should consist of 2500-3000 words. There should be the use of different forms of discourses, e.g. exposition, argumentation, description, and narrations. There should be an organization of the contents, relevance, and clarity in the essay"

Although one understands what these discourses are - and we use two discourses in an essay all the time e.g. descriptive (while defining) and argumentative (for rest of the current affairs essay mostly) - how is one able to write different (all of above) discourses in one essay?

Can you please suggest/advice how I can do that? some good examples would be much appreciated?

looking forward for you reply
Thanks

[TheAltruist]

It is not necessary that you use all the modes of discourses; you may notice 'should' in that sentence.