**Core Concept**
The question tests the diagnosis of a patient with a gallbladder stone, jaundice, and increased urobilinogen in the urine. This scenario involves the integration of liver function, bilirubin metabolism, and the consequences of a gallbladder stone.

**Why the Correct Answer is Right**
The patient's high urobilinogen in urine suggests an increase in bilirubin turnover and breakdown. With a serum bilirubin level of 2.5 mg%, the patient is likely experiencing a form of jaundice. The presence of a gallbladder stone could lead to obstructive jaundice if the stone is impacting the common bile duct. However, the high urobilinogen levels suggest a more significant issue with bilirubin metabolism, pointing towards a diagnosis of hemolytic jaundice. This is further supported by the patient's low hemoglobin level (HB-6 gm%). Hemolytic jaundice is characterized by increased breakdown of red blood cells, leading to elevated bilirubin levels and, consequently, increased urobilinogen in the urine.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
In cases of hemolytic jaundice, it's essential to investigate the underlying cause, which could be a genetic disorder, autoimmune disease, or infection.

**Correct Answer:** D.