Answer:
The correct answer is option b. "validity".
Step-by-step explanation:
Validity is essentially at which extent a concept, conclusion or measurement is well-founded and if the findings correspond to what is claimed in the research. In this example, professor Jenner used a definition of unemployment that did not match the one used by the Census Bureau, but he did used Census Bureau data to examine the trend of unemployment. Professor Jenner findings are not well-founded, therefore he is dealing with the issue of validity.