Which of the following describes a CNC machine?

A CNC (Computer Numerical Control) machine is defined as a fully automated machine that is controlled by a computer. This means that the operation of the machine—including cutting, milling, or any other machining process—is dictated by a computer program. The precision and repeatability of CNC machines stem from this computerized control, which allows for complex designs and consistent production that would be difficult to achieve with manual methods.

CNC machines eliminate much of the variability associated with human operation, making them essential in modern manufacturing where accuracy and efficiency are paramount. They enable manufacturers to produce parts that adhere closely to specifications, minimizing errors and waste.

In contrast, machines that are operated by hand or require skilled manual labor lack this automated and computer-controlled capability, often leading to more variations in the output. Additionally, basic machines used for sanding do not typically incorporate the advanced features of CNC technology, which can control multiple axes and perform intricate machining tasks. Therefore, the defining characteristic of a CNC machine is its computer-controlled automation, making option C the accurate description.