The professor told Hillary she would need to select a new topic for her speech because her current topic "How to plant an apple seed" would not engage the audience. Which characteristic of a speech topic is the professor talking about?
ambiguity
timeliness
appropriateness
substantive

The answer is appropriateness

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.

substantive

Explanation:

substantive—that it deal with matters of substance. Select a topic that is important enough to merit the time and attention of a group of intelligent people. Ask yourself: Would this topic engage the attention of my classmates? Would a reputable newspaper cover such a topic? Would students find this topic relevant to their social or professional lives?

i think the answer is c