**Core Concept**
The question is testing the knowledge of a single drug regimen for carcinoma esophagus that demonstrates a significant reduction in tumor size. This concept is relevant to the treatment of esophageal cancer, which often involves chemotherapy, radiation therapy, or a combination of both.

**Why the Correct Answer is Right**
The correct answer is **Paclitaxel**. Paclitaxel is a chemotherapy medication used to treat various types of cancer, including esophageal cancer. It works by inhibiting cell division, thereby preventing cancer cells from growing and multiplying. Paclitaxel has been shown to reduce tumor size in patients with esophageal cancer, with a response rate of around 15-20%.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not specify a single-drug regimen for carcinoma esophagus.
**Option B:** This option is incorrect as it does not accurately represent a chemotherapy medication used to treat esophageal cancer.
**Option C:** This option is incorrect as it does not demonstrate a significant reduction in tumor size.

**Clinical Pearl / High-Yield Fact**
Paclitaxel is a taxane-based chemotherapy medication that is also used to treat breast, lung, and ovarian cancers. It is often used in combination with other chemotherapy medications to enhance its effectiveness.

**Correct Answer:** C. Paclitaxel