What characterizes a synchronous change in a digital circuit?

A synchronous change in a digital circuit is characterized by the occurrence of changes at specific intervals controlled by a timing device, typically a clock signal. This means that all elements of the circuit that are governed by this timing device will change their states simultaneously based on the clock's edges (rising or falling).

This is essential for the proper functioning of synchronous circuits, ensuring that data is processed in a coordinated manner, which allows for predictable and reliable operation. By relying on a common clock, synchronous systems can effectively synchronize operations across multiple components, leading to improved efficiency in processing and communication between different parts of the circuit.

In contrast, the other options hint at asynchronous operations where timing is not strictly controlled by a clock signal, leading to potential mismatches in changes across different circuit elements. This lack of synchronization can cause timing issues and data integrity problems, which is why synchronous operation is favored in many digital design scenarios.