The teacher showed her ___________ about the student’s behaviors. A. disappoint B. disappointment C. disappointed D. disappointedly

The correct answer is B. disappointment.

In this context, the sentence is referring to the teacher's feelings or emotions regarding the student's behaviors. The word "disappointment" is a noun that signifies the feeling of sadness or displeasure caused by the non-fulfillment of one’s hopes or expectations.

The other options do not fit correctly in the blank due to their grammatical nature:
- A. disappoint: This is a verb that means to fail to fulfill someone’s hopes or expectations, and it does not fit as it would require a subject and would not appropriately modify the teacher's feelings.
- C. disappointed: This is an adjective that describes a feeling of dismay or unhappiness; it could potentially modify "the teacher," but the sentence requires a noun to follow "her."
- D. disappointedly: This is an adverb used to describe the manner in which an action is performed; it does not work in this context either, as it does not provide the noun needed for the structure.

Thus, only "disappointment" properly conveys the teacher's emotion in relation to the student’s behaviors in a grammatically correct manner.