The name of the button which Merlia needs to press to see how her transitions look is:
This is a type of feature which allows a person to view his work to see the progress made and see if there are any corrections to be made.
With this in mind, because Merlia is creating a presentation, then she has to use the preview button to see how the transitions which she has already made look.
Read more about preview here:
https://brainly.com/question/13171394