**Core Concept**
Suspicion of infidelity in a marital relationship is a complex psychological issue that requires a thorough evaluation of the underlying dynamics. The diagnosis of a husband's suspicion that his wife is having an affair falls under the category of a psychological disorder, specifically a type of anxiety disorder known as an **Othello syndrome** or morbid jealousy.

**Why the Correct Answer is Right**
Othello syndrome is characterized by an excessive and irrational preoccupation with the idea that one's partner is being unfaithful, often accompanied by feelings of anxiety, anger, and jealousy. This condition is typically triggered by perceived or actual threats to the relationship, such as infidelity, but can also be fueled by other factors like insecurity, low self-esteem, or past experiences. The husband's suspicion is likely driven by his own psychological vulnerabilities, rather than any concrete evidence of infidelity.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe the husband's situation. **Option B:** This option is too broad and could refer to a range of relationship issues, not specifically the husband's suspicion of infidelity. **Option C:** This option is incorrect as it implies that the diagnosis is related to the wife's behavior, rather than the husband's psychological response to perceived infidelity.

**Clinical Pearl / High-Yield Fact**
It's essential to differentiate between Othello syndrome and other conditions like paranoid personality disorder or factitious disorder, which may present with similar symptoms. A thorough psychological evaluation, including a detailed history and assessment of the husband's mental state, is crucial for an accurate diagnosis.

**Correct Answer: D. Othello syndrome**