Need more info, give the options?
A n environmental stressor could be;
the weather, too hot, say a heatwave, which can cause heat stroke, dehydration etc, or too cold, where vulnerable people may freeze to death, or develop frost bite etc.
So, some characteristic part of where we live which may, under certain conditions cause difficulty for us or some other living being.
Well, Assuming that this is the same multiple choice question that I have answered, I would say B. Chromosomal Disease.
