Final answer:
The item that breaks and leaves a pool on the floor dealing 8 damage per tick to enemies walking over it when Isaac takes damage is Lemon Mishap.
Step-by-step explanation:
The item that breaks and leaves a pool on the floor dealing 8 damage per tick to enemies walking over it when Isaac takes damage is A) Lemon Mishap. The Lemon Mishap is an activated item in the game The Binding of Isaac. When used, it creates a pool of lemon juice on the floor that damages enemies.