**Core Concept**
Executive magistrates are authorized to take cognizance of certain offenses and impose penalties, but their powers and roles are defined by law. To determine who cannot be an executive magistrate, we need to consider the legal framework governing their appointment and authority.

**Why the Correct Answer is Right**
In India, executive magistrates are typically police officers or government officials who have been empowered to exercise judicial functions in specific contexts. However, not all police officers or government officials have the authority to act as executive magistrates. The correct answer is someone who does not possess the requisite legal authority or qualifications to hold this position.

**Why Each Wrong Option is Incorrect**
**Option A:** A District Magistrate is a high-ranking government official who often serves as an executive magistrate, so this option is incorrect.
**Option B:** A Sub-Divisional Magistrate is also a government official who may be appointed as an executive magistrate, making this option incorrect.
**Option C:** A Judicial Magistrate is a judicial officer who has the authority to act as an executive magistrate in certain circumstances, so this option is incorrect.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the powers and roles of executive magistrates can vary depending on the jurisdiction and the specific context in which they are operating.

**Correct Answer:** D.