Correct answer: B. Selenium exposure.
Rationale
Helicobacter pylori infection is by far the most important risk factor for gastric cancer worldwide. Less common risk factors for gastric cancer include Lynch syndrome, Peutz-Jeghers syndrome, Menetrier's disease, and germline mutations in the CDH gene (encoding E-cadherin). However, there is some evidence that selenium, as well as high consumption of fruits and vegetables, may have protective effects against gastric cancer.
References
de Martel C et al. Gastroenterol Clin North Am. 2013 Jun;42(2):219-40.
Giardiello FM et al. N Engl J Med. 1987 Jun 11;316(24):1511-4.
Qiao YL et al. J Natl Cancer Inst. 2009 Apr 1;101(7):507-18.
