To answer this question, you need to understand the different operations related to machining processes.
Option A) Boring - This option is correct. Boring is the operation of enlarging a hole using a single-point cutting tool. It is commonly used to increase the size of an existing hole or to achieve a specific tolerance or surface finish.
Option B) Counter sinking - This option is incorrect. Counter sinking is the operation of creating a conical recess at the top of a hole to accommodate the head of a screw or bolt.
Option C) Drilling - This option is incorrect. Drilling is the operation of creating a hole in a workpiece using a rotating cutting tool called a drill bit.
Option D) Reaming - This option is incorrect. Reaming is the operation of finishing and sizing a hole that has already been drilled or bored, using a tool called a reamer.
The correct answer is A) boring. This option is correct because boring is the operation specifically used for enlarging a hole.