**Core Concept**
The question is testing the concept of a pharmaceutical technique used to mix two or more substances without mechanical stirring, resulting in a uniform mixture. This technique is crucial in pharmaceutical manufacturing, especially for powders or pastes.

**Why the Correct Answer is Right**
The correct answer is **C. Spheronization**. Spheronization is a process that transforms two or more fluid or paste-like materials into a homogeneous mixture without mechanical stirring. This is achieved by passing the mixture through a heated die or a rotating drum, which breaks down the particles and forms a uniform spherical shape. The process is commonly used in the production of tablets, especially for powders that are difficult to mix or for products that require a specific particle size distribution.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is not a recognized pharmaceutical technique for mixing substances.
* **Option B:** This option is not directly related to the mixing of substances without mechanical stirring.

**Clinical Pearl / High-Yield Fact**
Spheronization is a crucial step in the production of tablets, especially for powders that are difficult to mix or for products that require a specific particle size distribution. The process helps to achieve uniformity and increases the bioavailability of the active ingredient.

**Correct Answer:** C. Spheronization.