**Core Concept**
The question is related to the properties of gypsum, a material commonly used in dentistry for making dental casts and dies. Gypsum is a hydrated calcium sulfate, and its strength is affected by the amount of water used in its preparation. The **hydrate of the hemihydrate** refers to the chemical reaction involved in the setting of gypsum.

**Why the Correct Answer is Right**
The correct answer is related to the excess water left in the specimen after the hydration reaction is complete. This excess water can affect the strength of the gypsum specimen. When the water in excess of that required for the hydrate of the hemihydrate is left in the specimen, it can lead to a weaker specimen. The strength of the gypsum specimen under these conditions is an important consideration in dental materials.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the specific condition of excess water in the specimen.
**Option B:** This option is also incorrect as it does not relate to the specific condition described in the question.
**Option C:** This option is incorrect because it refers to a different property of gypsum.
**Option D:** This option is incorrect as it is not relevant to the condition described in the question.

**Clinical Pearl / High-Yield Fact**
The strength of gypsum specimens is crucial in dentistry, as it affects the accuracy and durability of dental casts and dies. Understanding the factors that affect the strength of gypsum, such as excess water, is essential for achieving optimal results in dental procedures.

**Correct Answer:** Correct Answer: D. Green strength.