Final answer:
Major depressive disorder is said to occur when signs of depression last at least two weeks. It is a long-term, debilitating illness that usually needs treatment to cure. Therefore, the correct option is C.
Step-by-step explanation:
When depressive symptoms persist for at least two weeks, it is considered to be major depressive disorder. It is a chronic, crippling condition that is typically curable with medical intervention.
In order to be diagnosed with major depressive disorder, an individual must have had symptoms such as a loss of enjoyment in previously enjoyed activities, changes in appetite and sleep schedules, difficulty concentrating, feelings of worthlessness, and sui*idal thoughts, in addition to a severely depressed mood lasting longer than two weeks.
Therefore, the correct option is C.