In the Diathesis-Stress Model, What Does "Stress" Refer To

In the diathesis-stress model, what does "stress" refer to?

A) life events that, in combination with an inherited tendency, trigger a disorder
B) inherited tendencies that, in combination with life events, trigger a disorder
C) the fact that without a diathesis, a disorder will not develop
D) exposure to very unusual and extreme environmental conditions, which trigger a disorder