**Core Concept**
Morphine dependence is a complex condition that involves physical and psychological dependence on the opioid. Treatment options aim to manage withdrawal symptoms, alleviate cravings, and prevent relapse. Various pharmacological agents are employed to achieve these goals.

**Why the Correct Answer is Right**
The treatment of morphine dependence involves medications that either block the effects of opioids or reduce cravings. Methadone is a long-acting opioid agonist used for maintenance therapy, while buprenorphine is a partial opioid agonist that helps reduce withdrawal symptoms and cravings. Naltrexone, on the other hand, is an opioid antagonist used to prevent relapse by blocking the effects of opioids. **Option A:** Methadone, **Option B:** Buprenorphine, and **Option C:** Naltrexone are all used in the treatment of morphine dependence.

**Why Each Wrong Option is Incorrect**
**Option D:** Clonidine is primarily used to manage withdrawal symptoms such as anxiety, agitation, and hypertension. Although it can be used as an adjunct in opioid withdrawal, it is not a primary treatment for morphine dependence.

**Clinical Pearl / High-Yield Fact**
When treating morphine dependence, it is essential to taper off the medication gradually to avoid withdrawal symptoms and ensure a smooth transition to maintenance therapy.

**Correct Answer:** D. Clonidine.