The correct answer is: D. each operation in a sequence is continuous, but subsequent operations in the sequence may be different.
A semi-continuous operation is a type of manufacturing process that is not fully continuous, but does have some continuous elements. In a semi-continuous operation, the workpiece is moved through a series of steps, each of which is performed continuously. However, there may be pauses between steps, or the workpiece may be moved to a different machine for the next step.
Option A is incorrect because it describes a continuous operation. In a continuous operation, the workpiece is moved through the process without interruption.
Option B is incorrect because it is not a requirement for a semi-continuous operation. Coffee breaks are allowed for operators in all types of manufacturing processes.
Option C is incorrect because a computer is not a required part of a semi-continuous operation. Some semi-continuous operations may use computers, but others may not.
Option E is incorrect because it is not a complete list of the possible characteristics of a semi-continuous operation.