**Core Concept**
Opium withdrawal is a condition that occurs when an individual who has developed physical dependence on opioids such as morphine, heroin, or codeine suddenly stops or significantly reduces their consumption. This leads to a complex interplay of neurotransmitter and hormonal changes in the brain.

**Why the Correct Answer is Right**
The correct answer is related to the symptoms of opium withdrawal, which typically include anxiety, agitation, insomnia, sweating, and gastrointestinal disturbances. These symptoms are primarily caused by the rebound effect of the body's attempt to restore the normal balance of neurotransmitters, particularly gamma-aminobutyric acid (GABA) and dopamine, which are affected by opioid use. Additionally, the release of hormones such as adrenocorticotropic hormone (ACTH) and cortisol is also altered during opium withdrawal.

**Why Each Wrong Option is Incorrect**
**Option A:** Yawning is not a characteristic symptom of opium withdrawal.
**Option B:** While nausea and vomiting can occur in opioid withdrawal, they are not the most common symptoms.
**Option C:** Muscle cramps are not typically associated with opium withdrawal.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that opium withdrawal can be managed with medications such as methadone or buprenorphine, which help to reduce the severity of withdrawal symptoms and facilitate a smoother recovery process.

**Correct Answer: C. Muscle cramps.**