题目内容：
根据下列文章,请回答题。UlcersEven though ulcers appear to run in families, lifestyle Plays more of a role than genetic(基因的)factors in causing the illness，according to a report in the April l3th issue of 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(溃疡)。Overall。61%of ulcer risk appears to be due to environmental factors，such as smoking，and the remainin9 39%is due to genes，according to Dr．Ismo Raiha of the University of Turkey and colleagues at the University of Helsinki，Finland．Some researchers had suggested that families may spread Helicobacter pylori(幽门螺旋菌)，the bacteria(细菌)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 ulcer．Both twins were more likely to develop an ulcer if the pair were genetically the same as compared with a pair of fraternal(由两受精卵发育而成的)twins，suggesting that there must be some genetic susceptibility(敏感性)to ulcer development．
However The risk was no greater in twins living together compared with twins living part，suggesting that shared exposure to H．pylori was not to blame．“Environmental effects were not due to factors shared by family members，and they were related to smoking and stress in men and the use of pain—releasing medicines in women。”The authors write in their report．The report attributes the risk of men developing an ulcer partly to A．smoking and stres
B．the kinds of food they ea
C．the size of the famil
D．the use of certain medicine
参考答案：
答案解析：