题目内容：
根据以下短文，回答题。第三篇 Ulcers
Even though ulcers appear to run in families, lifestyle plays more of a role than genetic factors in causing the illness, according to a report in the April 13th Journal of Internal Medicine. In particular, smoking and stress in men and the regular use of pain-releasing medicines in women were linked with an increased risk of developing an ulcer.
Overall, 61% of ulcer risk appears to be due to environmental factors, such as smoking, and the remaining 39% is due to genes according to Dr. Ismo Raiha of the University of Turky and colleagues at the University of Helsinki, Finland. Some researchers had suggested that families may spread Helicobacteria pylori, the bacteria that can cause ulcers. However, the new study suggests this is unlikely, according to the report.
Raiha and colleagues studied data from more than 13,000 pairs of twins "to examine the roles of genetic and environmental factors in the origin of peptic ulcer disease," they explain. Both twins were more likely to develop an ulcer if the pair were genetically the same as compared with a pair of fraternal twins, suggesting that there must be some genetic susceptibility to ulcer development.
However, the risk was no greater in twins living together compared with twins living apart, suggesting that shared exposure to H. pylori was not to blame. "Environment effects were not due to factors shared by family members, and they were related to smoking and stress in men and the use of analgesics in women," the authors wrote. "The minor effects of shared environment to disease liability do not support the concept that the grouping of risk factors, such as H. pylori infection, would explain the genetic factor of peptic ulcer disease," they concluded.
According to the passage, which of the following is a very likely cause of ulcer in men?
A) Smoking and stress.
B) Drinking and smoking.
C) Genes and children.
D) Use of a certain medicine.
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