Final answer:
Developers are primarily responsible for carrying out Unit Testing, which focuses on verifying the functionality of individual components within the software.
Step-by-step explanation:
The testers of Unit Testing are primarily C.) Developers. During the development phase, developers are responsible for creating and executing unit tests to ensure that individual components of the software work as intended. These tests are focused on small, isolated sections of the codebase and are usually run frequently to catch any issues early in the development process. While other parties such as business analysts, customers, and independent testers can be involved in different stages of testing, unit tests are typically written and executed by the developers who wrote the code.