The answer is study if not I apologize
The Answer to this problem would be...
A. Under-coverage.
Using mobile phones has lots of advantages and disadvantages and most you will be aware of that. Earlier days, when we are out of home or office, we need to search for a public telephone booth to make a phone call, but now, just pick up your mobile phone and dial. I am trying to list the Pros and cons of using a mobile phone in this post. Advantages of using a mobile phone You are always connected, anybody who knows your mobile number can contact you. If you are travelling out of your territory...
I believe that the correct answer is C because that literally shows it, but it also could be A because that is a more accurate detail that she actually missed it, and that it wasn't just a random bus. But, I think it is most likely A because C is just imagery. Hope this clarified it a little bit!