What type of assessment specifically measures knowledge that has been attained as well as knowledge that has not yet been acquired?

The correct answer focuses on the nature of the assessment, which is designed to measure both what a learner has achieved and what they still need to work on. A criterion-referenced test evaluates the performance of a student against a predetermined standard or criterion. It indicates not only the student’s current knowledge and skills but also identifies specific areas that require further development.

In contrast, other assessment types may not provide a comprehensive view of both attained knowledge and gaps in learning. For example, a behavior rating scale typically focuses on specific behaviors rather than academic knowledge, and while formal assessments often measure learning, they might not explicitly aim to identify knowledge gaps in the same way a criterion-referenced test does. A diagnostic measure can assess a learner's current level but is often more focused on identifying specific learning difficulties rather than measuring overall knowledge against set criteria.

Thus, the nature of a criterion-referenced test makes it particularly effective for determining both what has been learned and what still requires attention, making it the most fitting choice for the assessment described in the question.