Correct option is B
In the step turning process, the primary requirement is to remove material and produce different diameters (steps) on a workpiece using a lathe. The essential tools for actually performing this operation are cutting tools, such as the turning tool (for machining steps) and sometimes a parting tool (for cutting shoulders or separating parts).
A Vernier caliper, however, is not required to perform the operation itself. It is only a measuring instrument, used after or during machining to check the dimensions and ensure accuracy. The machining process can still be carried out without it, although measurement accuracy would be affected.
On the other hand, tools like the turning tool and parting tool are directly involved in material removal, making them essential for the process.
