**Core Concept**
The co-efficient of thermal expansion (CTE) of dental amalgam refers to its ability to expand or contract in response to temperature changes. This property is crucial in dentistry as it affects the amalgam's interaction with the surrounding tooth structure and the potential for tooth fracture or restoration failure.

**Why the Correct Answer is Right**
The correct answer is 14 ppm/°C. This value is relatively high compared to other dental restorative materials, indicating that amalgam undergoes significant expansion and contraction with temperature changes. This property is due to the thermal expansion of the mercury component, which makes up about 50% of the amalgam mixture. The high CTE of amalgam can lead to microleakage and marginal breakdown over time, especially in areas with significant temperature fluctuations.

**Why Each Wrong Option is Incorrect**
**Option A:** This value is too low, as it would imply that amalgam has a low thermal expansion coefficient, which is not the case.
**Option B:** This value is not accurate for dental amalgam and may refer to another material.

**Clinical Pearl / High-Yield Fact**
Dental amalgam's high CTE can be mitigated by using a proper matrix system and ensuring adequate condensation to minimize microleakage.

**Correct Answer:** C. 14 ppm/°C.