**Core Concept**
Theophylline poisoning is a life-threatening condition requiring prompt management. The drug of choice for treating theophylline toxicity is a medication that can effectively counteract its adverse effects, particularly those related to its inhibition of cytochrome P450 enzymes and its agonistic activity at adenosine receptors.

**Why the Correct Answer is Right**
The correct answer is **Activated Charcoal**. Activated charcoal is the drug of choice in theophylline poisoning due to its ability to adsorb and reduce the absorption of the toxin from the gastrointestinal tract. This can help decrease the peak plasma concentration of theophylline and reduce the severity of its adverse effects. In addition, activated charcoal has a large surface area and can effectively bind to theophylline, making it less available for absorption into the bloodstream.

**Why Each Wrong Option is Incorrect**
**Option A:** **Hemodialysis** is not effective in theophylline poisoning because theophylline has a large volume of distribution, making it difficult to remove through dialysis. Hemodialysis may be considered in severe cases, but its effectiveness is limited.

**Option B:** **Flumazenil** is a benzodiazepine antagonist and is not relevant to the treatment of theophylline poisoning. Theophylline does not have significant central nervous system effects that would require reversal with flumazenil.

**Option C:** **Sodium bicarbonate** may be used to treat severe theophylline-induced hypokalemia, but it is not the primary treatment for theophylline poisoning.

**Clinical Pearl / High-Yield Fact**
In theophylline poisoning, activated charcoal should be administered as soon as possible, ideally within 1 hour of ingestion, to maximize its effectiveness in reducing absorption.

**Correct Answer: A. Activated Charcoal**