**Core Concept**
Delusions are fixed, false beliefs that are not amenable to change in light of conflicting evidence. They are a hallmark of psychotic disorders, such as schizophrenia, and can also be seen in other conditions like bipolar disorder and severe depression.

**Why the Correct Answer is Right**
The correct answer is likely to be a condition where delusions are less common or not a characteristic feature. In the context of the options provided, delusions are not typically seen in **Depressive Disorder**. Depressive disorders are characterized by mood disturbances, anhedonia, and changes in appetite or sleep, but not fixed false beliefs. This is because the pathophysiology of depression involves altered neurotransmitter levels, particularly serotonin and norepinephrine, which do not typically lead to the development of delusions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, but it could potentially be a condition where delusions are common, such as schizophrenia or bipolar disorder. In these conditions, delusions are a characteristic feature and can be seen in a significant proportion of patients.
**Option B:** This option is not provided, but it could potentially be a condition where delusions are not as common, such as anxiety disorders. However, anxiety disorders can sometimes co-occur with psychotic disorders, where delusions may be present.
**Option C:** This option is not provided, but it could potentially be a condition where delusions are common, such as schizophrenia or bipolar disorder.

**Clinical Pearl / High-Yield Fact**
It's worth noting that delusions can sometimes be seen in non-psychotic disorders, such as severe medical illnesses or substance-induced psychosis. In these cases, the delusions are often transient and may resolve with treatment of the underlying condition.

**Correct Answer: D. Depressive Disorder**