What type of fasteners are described as self-tapping screws?

Self-tapping screws are designed to create their own threads in the material they are being driven into, which is why the description as hardened fasteners that create their own threads is accurate. These screws have a sharp tip and thread profile that allows them to cut into the material as they are inserted, effectively forming a tight fit without the need for a pre-drilled hole. This characteristic makes them effective in various applications where speed and ease of installation are crucial, such as in metal and plastic components.

The other descriptions do not accurately capture the unique functionality of self-tapping screws. For instance, while some fasteners do require pre-drilled holes, self-tapping screws do not; they are designed to work without such preparation. Additionally, the statement about only working with soft materials is misleading, as self-tapping screws can be utilized in various materials, including metal, depending on their design and coating. Lastly, the notion that they must be removed with special tools does not apply, as self-tapping screws can typically be removed with standard tools like a screwdriver or drill. Therefore, the defining feature of self-tapping screws is their ability to create threads in the material they penetrate, making option B the correct choice.