**Core Concept**
High speed in dentistry refers to the rotation speed of dental handpieces, which is crucial for efficient and safe drilling, cutting, and other procedures. The speed of these handpieces is typically measured in revolutions per minute (RPM).

**Why the Correct Answer is Right**
The correct answer, **50000-100000 RPM**, is the range that defines high-speed drilling in dentistry. This speed range allows for efficient removal of tooth structure, while also minimizing the risk of heat generation and potential damage to the surrounding tissues. High-speed handpieces are designed to operate within this range, taking advantage of the optimal balance between speed and torque to perform various dental procedures accurately and safely.

**Why Each Wrong Option is Incorrect**
**Option A:** 20000-50000 RPM is considered low speed in dentistry, often used for procedures that require more control and precision, such as cavity preparation in non-vital teeth or in pediatric dentistry.

**Option C:** 100000-200000 RPM is considered ultra-high speed, which is typically reserved for specialized procedures like endodontic treatment or in orthodontic tooth movement, where precise and controlled cutting is required.

**Option D:** Above 200000 RPM is not a standard classification in dentistry, as the rotation speed of handpieces is limited by the design and materials used in their construction.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the choice of speed for dental handpieces depends on the specific procedure, the type of tooth structure being worked on, and the dentist's personal preference. Always refer to the manufacturer's guidelines for the recommended speed range for each handpiece.

**✓ Correct Answer: B. 50000-100000. This speed range is optimal for high-speed drilling in dentistry.**