**Core Concept**
Phacomelia is a rare congenital disorder characterized by the absence or severe underdevelopment of the limbs, particularly the radius and ulna bones in the forearm. This condition is associated with exposure to certain teratogenic agents during embryonic development.

**Why the Correct Answer is Right**
The correct answer is associated with the teratogenic effects of a specific drug on limb development. The drug in question is a thalidomide analogue, which was previously used as an antiemetic and sedative. Thalidomide is known to interfere with the normal development of limbs by inhibiting the growth of limb buds. This occurs due to the disruption of the sonic hedgehog (SHH) signaling pathway, which is crucial for the development of the limbs.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not directly relate to the teratogenic effects on limb development.
* **Option B:** This option is incorrect because it does not specifically address the phacomelia deformity.
* **Option C:** This option is incorrect because it is not directly associated with the disruption of limb development.

**Clinical Pearl / High-Yield Fact**
Thalidomide is a classic example of a teratogenic agent that can cause severe limb abnormalities, including phacomelia, when administered during early pregnancy.

**Correct Answer: C. Thalidomide**