## **Core Concept**
The question pertains to the specifics of endodontic files, particularly the taper present in a size 20 GT (Gates Glidden) file. Endodontic files are instruments used in root canal treatments to clean and shape the canal. The taper of an endodontic file refers to the increase in diameter of the file along its length, usually expressed as a ratio (e.g., 0.02 or 2%).

## **Why the Correct Answer is Right**
The correct taper for endodontic files, including GT files, is typically standardized. Most endodontic files have a standard taper of 0.02 (or 2%), which means that for every millimeter of length, the diameter of the file increases by 0.02 mm. This taper allows for efficient cleaning and shaping of the root canal while minimizing the risk of canal transportation or perforation. Therefore, the correct answer indicating a taper of 0.02 (or 2%) is right because it aligns with the standard taper for endodontic files, including size 20 GT files.

## **Why Each Wrong Option is Incorrect**
- **Option A:** If this option suggests a taper other than 0.02 (e.g., 0.01 or 1%), it would be incorrect because it does not match the standard taper for endodontic files.
- **Option B:** Similarly, if this option suggests a different taper (e.g., 0.03 or 3%), it would not be standard for GT files or most endodontic files.
- **Option D:** This option would also be incorrect if it suggests any taper that does not match the standard 0.02 (2%) taper.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the standard taper for most endodontic files, including GT files, is **0.02 (2%)**. This standardization helps in ensuring that the files are used appropriately for cleaning and shaping root canals, reducing the risk of complications.

## **Correct Answer:** . **0.02**