Answer: A
C49.A2 is the correct code for this case because it codes for the gastrointestinal stromal tumor of the stomach. All the symptoms of abdominal pain for a few months, that suggests it is a tumor of the stomach.
Option B is not correct because C49.A9 is used to code for gastrointestinal stromal tumor of the other sites.
Option C is not correct because C49.A0 is used to code for gastrointestinal stromal tumor, unspecified site.
Option D is not correct because C49. A5 is used to code for the gastrointestinal stromal tumor of the rectum.