**Core Concept**
The restoration of choice for a class V cavity involves a gold alloy, specifically an inlay made of a gold-based material. This type of restoration is preferred for its durability and biocompatibility. The gold alloy used in dental restorations is a mixture of gold with other metals, such as silver, copper, and zinc.

**Why the Correct Answer is Right**
The gold alloy used in dental restorations, including class V inlays, typically contains 75% gold. This high gold content provides the necessary strength and durability for the restoration, while also being biocompatible with the surrounding tooth structure. The remaining 25% is composed of other metals, such as silver, copper, and zinc, which help to strengthen the alloy and prevent corrosion.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately represent the gold content of the gold alloy used in dental restorations.
**Option B:** This option is incorrect because it is too high and would not be practical for use in dental restorations.
**Option C:** This option is incorrect because it is too low and would not provide the necessary strength and durability for the restoration.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the gold content in dental restorations can vary depending on the specific alloy used, but 75% gold is a common and widely accepted standard for class V inlays.

**Correct Answer: A. 75%**