Answer:
The answer is appropriateness
Step-by-step explanation:
Appropriateness of a speech describes how an audience in a specific social context perceive a speech as being suitable or proper. On the other hand, speech engagement (from the root word engage) is the measure of how well a speech grabs the attention of an audience.
Therefore, if a speech is appropriate for a particular audience in a social context, they would find it engaging and pay full attention to it. On the other hand, if the speech has elements of inappropriateness (the opposite of appropriateness) it wouldn't grab the attention of an audience.
Remember one of the reasons of delivering speech is to capture the attention of an audience. That is why the professor asked Hillary to consider selecting a new topic that would engage (grab the attention) of her audience.