B. We hear Oberon describe what the juice from the flower does to Puck (when you put it on the eyes of someone sleeping, they'll fall in love with whatever they see first when they wake). He tells Puck his plan and is so excited for her to fall in love with any type of monster or wild animal that comes across her path and wakes her up. Puck then uses this inspiration to turn Bottom into a Donkey when he knows he will be the first thing Titania sees when she wakes up.
This is dramatic irony because Oberon, Puck, and the audience all know what's going to happen as soon as she opens her eyes and sees Bottom, but Titania has no idea.
