**Core Concept**
The question pertains to the physical properties of wax, specifically its melting point and the temperature range at which it can be softened for use in medical procedures, such as casting or molding impressions.

**Why the Correct Answer is Right**
The ideal temperature for softening fluid wax is between 90°C to 100°C. This temperature range is critical because it is just below the melting point of the wax, allowing it to be pliable and easily shaped without becoming too hot to handle. At this temperature, the wax molecules begin to gain kinetic energy, making it more fluid and easier to manipulate. **Option C** is the correct answer because it falls within this optimal temperature range.

**Why Each Wrong Option is Incorrect**
**Option A:** This temperature is too low, and the wax will not be soft enough for effective manipulation.
**Option B:** This temperature is too high, and the wax will melt excessively, becoming difficult to handle and potentially causing burns.
**Option D:** This temperature is also too low, and the wax will not reach its optimal softening point, leading to a suboptimal impression or casting.

**Clinical Pearl / High-Yield Fact**
When working with wax in a medical setting, it is essential to maintain a consistent temperature to ensure consistent results and prevent accidents.

**Correct Answer: C. 98°C**