Which of the following means 'exists at time of acceptance and cannot be discovered by a reasonable inspection'?

An undetectable fault implies a defect that cannot be found by any means, but it does not specifically relate to the timing of acceptance or reasonable inspection. A fault may be undetectable due to various reasons, but it doesn't inherently imply that it existed at the time of acceptance or that it could be discovered later.

A hidden defect is similar to a latent defect but typically refers to a problem that is concealed and not easily seen. However, the term does not necessarily encompass the aspect of being present at the time of acceptance or the inability to discover it during a reasonable inspection.

This phrase refers to defects that are found during the inspection process. Unlike latent defects, which remain hidden until later, discovery incident to inspection indicates that the flaws are revealed during the inspection itself, contradicting the premise of being undiscoverable at acceptance.