Answer:She decides that her first main point should provide a definition of invasive species.
Step-by-step explanation:
A definition refers to a meaning of a term or word or phrase , it provides a clear understanding of what the term means , it can be intensional when it gives a reasonable clue of what the term means and an extensional definition if person further mentions or give examples of objects associated or that are described by that term.
In this case Abby's audience may not be aware of what invasion species are but as she explains this and give examples people will begin to grasp what she is about to talk about and may want to hear more.