The option with the commas is the best written sentence
I am in karachi, because Karachi is a city and you can't be "at" a city. Saying I'm at only works if it a place such as a grocery store or a mall, but does not apply to cities or countries.
A B And c Should Work Hope I Helped
The best strategy is credit the sites you go to
hope this helps
-rachael
(yahtzee05)