Which tool is specifically for cutting inside threads?

The tool specifically designed for cutting inside threads is known as a nut tap. This is because a nut tap is specifically shaped and sized to create the internal threads of nuts or similar components. Nut taps have a taper to help with threading, and their design allows them to be used effectively within confined spaces. This is essential for accurately creating internal threads for bolts or screws to fit into.

The other options, while related to threading, do not specifically address the need for cutting internal threads. A screw tap is typically referred to for creating threads in holes for screws, but the specific context of a nut tap directly applies to the creation of internal threads, which makes it the most suitable answer for this question.