Final answer:
Gastric ulcers are mainly caused by the bacterium Helicobacter pylori and the chronic use of NSAIDs. Spicy food, acidic food, and stress do not directly cause gastric ulcers.
Step-by-step explanation:
Gastric ulcers are primarily caused by the bacterium Helicobacter pylori. This bacterium is able to tolerate the acidic environment of the stomach and can lead to the development of ulcers. Other factors, such as the chronic use of non-steroidal anti-inflammatory drugs (NSAIDs), can also contribute to the formation of peptic ulcers. Contrary to popular belief, factors like spicy food, acidic food, and stress do not directly cause gastric ulcers.