Which of the following is a common symptom of gastric cancer?

Hematemesis, which refers to vomiting blood, is a common symptom of gastric cancer due to the potential for tumors to cause bleeding in the stomach lining. As gastric cancer progresses, it can lead to ulceration or erosion of the stomach's blood vessels, resulting in this critical symptom. Vomiting blood is an alarming sign that necessitates immediate medical evaluation, as it can indicate significant complications associated with malignancies like gastric cancer.

Other potential symptoms, such as indigestion, may occur but are often more associated with benign gastrointestinal issues or less severe conditions. Sharp pain in the groin is not typically related to gastric cancer, as this type of cancer primarily affects the stomach and does not usually manifest in such a manner. Chronic diarrhea is also less indicative of gastric cancer specifically; it often points to other gastrointestinal disorders. Thus, hematemesis stands out as a more direct and alarming symptom associated with the malignancy, making it the correct answer in identifying a common symptom of gastric cancer.