Correct option is A
Threading is a machining operation used to produce helical grooves on the external or internal surface of a cylindrical job. These grooves form the threads that allow components like bolts and nuts to engage and fasten together. The helical shape ensures smooth engagement and load distribution along the thread length.
Other options like V-shaped or rectangular describe the profile of the thread, but the fundamental nature of threading is the creation of a helical path around the cylinder. Circular grooves are not correct because threads are not simple rings but continuous spirals.
