Which could be a source of false indications on a test specimen?

A source of false indications on a test specimen can indeed be contamination from the inspector's hands. When conducting tests on various materials, any residues, oils, or contaminants present on the inspector's hands can transfer to the specimen. This contamination can obscure the true condition of the specimen and may lead to incorrect readings or misinterpretations of the test results. For instance, if the test involves visual inspection or non-destructive testing methods, oils or dirt can mask defects or create false indications, giving the impression that there are flaws present when in fact there are not.

In contrast, while dry probes during testing, poor lighting conditions, and direct exposure to sunlight can impact testing outcomes, they pertain more to the conditions under which the tests are conducted rather than introducing contamination. Dry probes may fail to make proper contact, leading to inaccurate readings, poor lighting can hinder visibility and affect visual assessments, and sunlight can introduce glare or affect temperatures. However, these factors don’t bring external contaminants directly onto the test specimen, which is the key reason why contamination from the inspector's hands stands out as a significant concern for false indications.