**Core Concept**
The procedure of ventrolateral cordotomy is a surgical method used to relieve intractable pain by interrupting the transmission of pain signals to the brain. This is achieved by lesioning the **spinothalamic tract**, which is responsible for transmitting pain and temperature sensations. The spinothalamic tract is located in the **lateral** part of the **spinal cord**.

**Why the Correct Answer is Right**
To relieve pain in the right lower limb, the spinothalamic tract must be interrupted on the **contralateral** side of the pain, meaning the left side of the spinal cord. This is because the spinothalamic tract crosses to the opposite side of the spinal cord at the level it enters, via the **anterior white commissure**. Thus, to affect the right lower limb, the procedure should target the left ventrolateral cord.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not specify the correct side or location for the procedure.
**Option B:** Incorrect as it does not accurately describe the target for pain relief in the right lower limb.
**Option C:** Incorrect because, although it mentions the correct side, it lacks specificity regarding the target tract.
**Option D:** Incorrect as it does not correctly identify the side or the precise location for the procedure.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the spinothalamic tract crosses at the level of entry, so to relieve pain on one side of the body, the cordotomy must be performed on the opposite side of the spinal cord. This is crucial for the procedure's success.

**Correct Answer:** D. Left ventrolateral cord.