Which of the following is an example of non-vocal assent?

Non-vocal assent refers to a form of agreement or approval that does not involve spoken language. In this case, smiling at the therapist can indicate a positive acknowledgment or willingness to engage in an activity or session, making it a clear example of non-vocal assent. The smile serves as a non-verbal cue expressing consent or comfort with the situation.

The other options depict various reactions that do not signify agreement. Pushing materials away, for example, indicates rejection or refusal rather than consent. Crying and turning away also express distress or disinterest and are not indicative of assent. Lastly, while expressing frustration verbally shows a reaction to the circumstances, it does not communicate agreement or willingness. Therefore, smiling at the therapist is the only option that clearly represents non-vocal assent.