Which command is used to start the Unittest Test Runner?

The command used to start the Unittest Test Runner is formulated as "python -m unittest." This command leverages the -m option, which enables you to run a library module as a script. In this case, unittest is the module and the command initiates the test runner, allowing you to execute a suite of tests defined in Python files or classes that import the unittest module.

This approach to running tests is important because it allows for flexible test discovery across different directories and can handle various command-line arguments that the unittest framework supports. By running it this way, you can simply specify the directory or specific test files you want to run, making it a powerful command for executing test suites within a project.

The other commands do not accurately initiate the Unittest Test Runner in the standardized way. For instance, "python3 run unittest" is not a valid command structure for initiating the test runner, while "python unittest.main()" would typically be part of a script rather than a command to run directly from the command line. The "python run tests" command lacks the necessary syntax to engage the unittest module effectively, further distinguishing option B as the proper command to use.