## Core Concept
The question pertains to the concept of **enantiomers** in pharmacology, which are pairs of molecules that are mirror images of each other but are not superimposable. This concept is crucial in understanding **stereochemistry** and its impact on drug action.

## Why the Correct Answer is Right
The correct answer, , implies that 50% of the drug exists as an enantiomer. This is because a racemic mixture, commonly encountered in pharmaceuticals, consists of equal amounts (50:50) of two enantiomers. This mixture is optically inactive and is denoted by the symbol . The presence of enantiomers is significant because they can have different pharmacological and toxicological effects.

## Why Each Wrong Option is Incorrect
* **Option A:** This option suggests a different ratio, which does not accurately represent a racemic mixture.
* **Option B:** This option implies a different percentage, which is not characteristic of a racemic mixture.
* **Option D:** This option also suggests an incorrect ratio, not representative of a racemic mixture.

## Clinical Pearl / High-Yield Fact
A key point to remember is that many drugs are administered as racemic mixtures, but the body can metabolize or interact with the enantiomers differently. For example, **thalidomide**, which was famously used for its sedative properties but led to severe birth defects, exists as enantiomers that interconvert in the body, leading to different effects.

## Correct Answer Line
**Correct Answer: C. **