When you are speaking of or for yourself, use "am." When you are talking about a person or a thing (in the singular), use "is." When you are talking to a person, and when you are talking about other people or things (in the plural), use "are." Here, it is talking about a single thing. Hence, is will be used.
Stammer means speak with sudden involuntary pauses and a tendency to repeat the initial letters of words. The word after comma is 'but' which makes it obvious that the person did the opposite of what was supposed. Option D is correct.
We have been in Sector: 8, Gandhinagar . . . . . . . 1997.