**Core Concept**
Frotteurism is a paraphilic disorder characterized by recurrent and intense sexual urges to touch or rub against a non-consenting person, often in crowded areas or public places. This behavior is typically associated with an exhibitionistic personality type. The underlying psychological mechanism involves a distorted sense of entitlement to touch others, often fueled by feelings of powerlessness or inadequacy.

**Why the Correct Answer is Right**
The correct answer, C. Pleasure in touching opposite sex, accurately describes the core feature of frotteurism. Individuals with this disorder derive sexual gratification from non-consensual physical contact with others, often in a public or semi-public setting. This behavior is typically accompanied by a sense of excitement or arousal, which can be intense enough to drive the individual to engage in repeated acts of frotteurism despite the risk of detection and negative consequences. The behavior is often linked to underlying psychological issues, such as a need for control or a desire to assert power over others.

**Why Each Wrong Option is Incorrect**
**Option A:** Pleasure in watching intercourse is more accurately descriptive of voyeurism, another paraphilic disorder characterized by a desire to observe others engaging in sexual activity without their consent.
**Option B:** Pleasure in using article of opposite sex is not a recognized paraphilic disorder and does not accurately describe frotteurism.
**Option D:** Pleasure in wearing opposite sex clothes is more accurately descriptive of transvestic fetishism, a paraphilic disorder characterized by a desire to wear clothing typically associated with the opposite sex.

**Clinical Pearl / High-Yield Fact**
It's essential to note that individuals with paraphilic disorders, including frotteurism, may not necessarily engage in overtly aggressive or violent behavior. However, their actions can still cause significant distress and trauma to their victims, and may warrant psychological evaluation and treatment.

✓ Correct Answer: C. Pleasure in touching opposite sex