Final answer:
For a diagnosis of Major Depressive Disorder, at least 5 out of 9 symptoms must be present within a 2-week period according to diagnostic criteria (option a).
Step-by-step explanation:
In diagnosing Major Depressive Disorder (MDD), there must be at least 5 out of 9 symptoms present within a 2-week period. This conforms to the criteria set forth in various diagnostic manuals for cognitive health conditions such as the DSM-5. The symptoms associated with Major Depressive Disorder may include a persistent feeling of sadness or a loss of interest in activities once enjoyed, significant weight loss or gain, insomnia or hypersomnia, fatigue or loss of energy, feelings of worthlessness or excessive guilt, reduced ability to think or concentrate, and recurrent thoughts of death.
Hence, the answer is option a.