**Core Concept**
Stomach carcinoma, also known as gastric cancer, is a malignant tumor that arises from the epithelial cells of the stomach. It is a common cause of cancer-related mortality worldwide, with a higher incidence in developing countries. The clinical presentation of stomach carcinoma can vary, but it often involves weight loss, abdominal pain, and gastrointestinal bleeding.

**Why the Correct Answer is Right**
Weight loss is indeed the most common presenting feature of stomach carcinoma. This is due to the tumor's ability to infiltrate and obstruct the stomach, leading to malabsorption of nutrients and a decrease in appetite. Additionally, the tumor can cause an increase in gastrin production, which can lead to gastric overproduction and subsequent weight loss. The other options are incorrect because while weight loss is a common feature, it is not the only symptom, and secondaries are indeed commonly seen in the peritoneum and omentum. Lymphatic and hematogenous spread are also not rare, as the tumor can metastasize to regional lymph nodes and distant organs such as the liver and lungs.

**Why Each Wrong Option is Incorrect**
**Option B:** While secondaries can indeed be seen in the peritoneum and omentum, this is not the most common site of metastasis. The liver and lungs are more common sites of metastasis.
**Option C:** Lymphatic and hematogenous spread are not rare in stomach carcinoma. In fact, the tumor can metastasize to regional lymph nodes and distant organs through these routes.
**Option D:** Barium meal may show irregularities in the stomach mucosa or a filling defect, but it is not diagnostic for stomach carcinoma. Biopsy and histopathological examination are necessary for a definitive diagnosis.

**Clinical Pearl / High-Yield Fact**
Stomach carcinoma often presents with non-specific symptoms, and a high index of suspicion is necessary for early diagnosis. A significant weight loss of more than 10% of body weight over a period of 6-12 weeks should raise suspicion of stomach carcinoma.

✓ Correct Answer: A. Weightloss is commonest feature