Framework comparison

Question

Hey all. Im doing a project in c#. It takes line of input from either a text file or cut and past. It then compares the lines of arrays. It sorts the lines then does a calculation on them and deletes redundant lines.
The thing is. Im not a good programmer and have just started. Im only familure with the .net framework so I decided to go with that. My project supervisor however is looking for a better reason.
So in contrast to the arrays part of my project could anyone give me a standing arguement for why I should use c# instead of java or php.
Thanks