To solve this question, the user needs to know about the basic terminologies and operations of a lathe machine.
The feed rate in a lathe machine refers to the distance that a cutting tool advances into the workpiece with each revolution of the lathe spindle. It is typically expressed in millimeters per revolution (mm/rev).
Option A is correct because feed rate is generally given in millimeters per revolution (mm/rev). This means that for every complete revolution of the lathe spindle, the cutting tool advances a certain distance along the workpiece.
Option B is incorrect because the feed rate is not typically given in millimeters per degree. Degrees are used to measure angles, not distances.
Option C is incorrect because simply giving the distance in millimeters does not take into account the number of revolutions of the lathe spindle that are required to move the cutting tool that distance.
Option D is incorrect because RPM (revolutions per minute) is a measurement of the speed of the lathe spindle, not the feed rate.
Therefore, the correct answer is:
The Answer is: A. mm per revolution