**Core Concept**
Negative staining techniques are used in microscopy to visualize the morphology of cells, microorganisms, or other structures by contrast against a dark background. This method involves the use of a dye that does not penetrate the cells or structures of interest, resulting in a darkly stained background that highlights the specimen.

**Why the Correct Answer is Right**
The correct answer is a negative staining technique that involves the use of a dye that does not penetrate the cells or structures of interest. This technique is useful for visualizing the morphology of cells, microorganisms, or other structures by contrast against a dark background. The mechanism of negative staining involves the use of a hydrophobic dye that does not penetrate the cells or structures, resulting in a darkly stained background that highlights the specimen.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is a type of positive staining technique that involves the use of a dye that penetrates the cells or structures of interest.
* **Option B:** This option is incorrect because it is a type of differential staining technique that involves the use of two or more dyes to differentiate between different structures or components.
* **Option D:** This option is incorrect because it is a type of fixation method that is used to preserve the morphology of cells or tissues, but it is not a staining technique.

**Clinical Pearl / High-Yield Fact**
Negative staining techniques are useful for visualizing the morphology of cells, microorganisms, or other structures by contrast against a dark background. This technique is particularly useful for identifying bacteria, yeast, or other microorganisms that do not take up stains.

**Correct Answer: C. Wright's stain is a negative staining technique used to visualize the morphology of bacteria.**