I was interested to read your teacher's comment about everyone using Ansel Adams style - I really don't believe that for a minute - Adams was a darkroom technician and an extremely good one - he spent a lot more time in the darkroom than he probably ever did taking an individual image, at least that is my understanding. You could emulate his style, but only if you are prepared to spend a lot of time in post-processing with Photoshop.
I am not sure from your posting whether the person, whose style you have to use, should be alive or dead, or does it matter. Also, does it have to be a photographer in an urban field, or can it be some other field - landscape, portrait, action, sports, etc. - because there are literally hundreds of styles to "imitate/use". How does your teacher define "urban"- landscape, people...? You noted that they have to be "distinct" - I am assuming that is the one you are supposed to imitate? I am not familiar with either Zack Arias or Chase Jarvis, but if their work attracts you, then I would say - go for it. Let us know some additional information and then maybe we can give you a more definitive response. Good luck in your assignment.
Cheers,
WesternGuy