Answer:
d. An abstract concept
Explanation:
Abstract concept: The abstract concept has no physical form and is defined as an idea or design that a person can understand. The fundamental constituent of human intelligence provides them the ability to understand, identify, and communicate abstract concepts. This is not necessary that an abstract concept is not real, they can be real apart from the fact that it can be documented.
Construct validity: It states that a test measures what it purports or claims to measure. The construct validity sub-sums every other kind of validity evidence.