## Core Concept
Inclusion bodies, also known as metachromatic granules or Babes-Ernst bodies, are characteristic features of certain bacteria that can be stained to reveal their presence. These granules are particularly associated with bacteria that produce toxins.

## Why the Correct Answer is Right
The correct answer, *C. Corynebacterium diphtheriae*, is right because this bacterium contains metachromatic granules, also known as Babes-Ernst bodies. These granules are visible under a microscope when stained with specific dyes, such as methylene blue or Neisser stain. The presence of these granules is a key diagnostic feature for *Corynebacterium diphtheriae*, the causative agent of diphtheria. The granules are involved in the production of diphtheria toxin.

## Why Each Wrong Option is Incorrect
* **Option A:** *Streptococcus pneumoniae* does not typically contain metachromatic granules. It is identified through other means, such as bile solubility and optochin sensitivity.
* **Option B:** *Bacillus anthracis* is identified by its characteristic boxcar-shaped bacilli and not by metachromatic granules.
* **Option D:** *Clostridium tetani* is identified by its terminal spore resembling a drumstick, not by metachromatic granules.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that the presence of metachromatic granules in *Corynebacterium diphtheriae* can be demonstrated using the Neisser stain. This is a rapid and useful diagnostic tool in clinical microbiology, especially in cases where diphtheria is suspected.

## Correct Answer: C. Corynebacterium diphtheriae