An instructor finds that the standard, formal assessment towards the end of a given course yields erratic learner scores over a broad spectrum. During the course, the instructor observed all of the learners progressing at about the same pace. In this situation, which of the following
is the MOST likely source of the results?

A.
The formal assessment lacks validity.

B.
The formal assessment lacks reliability.

C.
The observation lacked validity.

D.
The observation lacked reliability.