Explanation: Environmental factors such as stress, trauma, infections, and certain medications are considered triggers that can worsen psoriasis symptoms in individuals who are already genetically predisposed to the condition. These triggers can lead to psoriasis flare-ups or worsen existing plaques.

Incorrect choices: a. Primary cause of psoriasis: Environmental factors are not the primary cause of psoriasis. While they can influence the severity of symptoms, the condition itself is primarily driven by genetic factors and immune system dysfunction.

b. Minor role with no significant impact: Environmental triggers are not minor in psoriasis etiology. They can have a significant impact on symptom severity and recurrence in susceptible individuals.

d. Protective factors against developing psoriasis: Environmental factors are not protective against developing psoriasis. As an autoimmune condition, psoriasis is primarily influenced by genetic predisposition and immune system dysfunction, not by protective environmental factors.