Which of the following describes an invalid class in equivalent partitioning?

In equivalent partitioning, the concept involves dividing input data into partitions that can be treated similarly because they produce the same results. An invalid class specifically refers to input values that are not accepted by the system or that result in an error or unexpected behavior.

When considering the choices, values that trigger errors represent conditions where inputs fall outside the acceptable range or criteria defined for the system under test. This means they effectively represent an invalid scenario, as they do not produce valid or expected outputs. Identifying these invalid classes is crucial for ensuring that error handling is tested appropriately, and that the application behaves as expected under failure conditions.

The other options represent valid or desirable outcomes rather than invalid classes. Therefore, focusing on where errors occur allows for a more comprehensive testing strategy that accounts for not just the success paths, but also the potential failure modes of the software.