## **Core Concept**
The question tests knowledge of chemotherapy administration methods, specifically focusing on agents that require continuous infusion. Continuous infusion is often used for drugs with a short half-life or those that require a steady concentration to be effective.

## **Why the Correct Answer is Right**
5-Fluorouracil (5-FU) is a chemotherapeutic agent commonly used in the treatment of various cancers, including colorectal, breast, and skin cancers. It works by inhibiting thymidylate synthase, which is crucial for DNA synthesis. Due to its short half-life, 5-FU is most effectively administered via continuous infusion to maintain a steady plasma concentration, enhancing its therapeutic efficacy while minimizing toxicity.

## **Why Each Wrong Option is Incorrect**
* **Option A:** Although some chemotherapy agents are administered via continuous infusion, without the specific name, it's hard to assess its accuracy. However, it's not the most commonly associated with continuous infusion compared to 5-FU.
* **Option B:** Similarly, without specifics, it's challenging to evaluate its correctness directly, but it's not the agent most commonly linked with continuous infusion.
* **Option C:** This option might refer to another chemotherapeutic agent, but again, specifics are needed for a direct assessment. It's not the correct answer based on the provided information.
* **Option D:** This could be another agent, but like the other options, without details, it's hard to directly refute its incorrectness aside from knowing 5-FU is the correct answer.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that 5-Fluorouracil (5-FU) is often administered via continuous infusion to achieve optimal therapeutic effects. This method helps in maintaining a steady drug concentration, which is critical for its mechanism of action and for minimizing side effects.

## **Correct Answer:** D. 5-Fluorouracil.