The correct answer is: C. one operator is needed for each machine.
Numerical control (NC) is the automation of machine tools that are operated by numerical control (NC) instructions. An NC machine tool is a machine tool that is controlled by a computer. The computer reads a program of instructions that tells the machine tool how to move and what to do. NC machines are used to make a variety of products, including parts for cars, airplanes, and appliances.
One disadvantage of NC machines is that one operator is needed for each machine. This is because NC machines are complex and require a lot of attention. The operator must monitor the machine and make sure that it is operating correctly. If the machine malfunctions, the operator must be able to diagnose the problem and correct it.
The other options are not disadvantages of NC machines. Option A is incorrect because computers are very reliable. Option B is incorrect because tape and tape readers are also very reliable. Option D is incorrect because machine tools are designed to withstand high temperatures. Option E is the correct answer because it is the only option that is a disadvantage of NC machines.