Final answer:
A child who believes medicine can revive a dead cat is likely between three to seven years old, displaying a phase of magical thinking typical of early childhood development.
Step-by-step explanation:
The age of a child who says, "My cat died, but if I get her some medicine, she will feel better tomorrow," is most likely preschool to early elementary school, commonly ranging from three to seven years old. This age group is often characterized by what is known in developmental psychology as magical thinking, where children believe that their thoughts can affect the world in ways that defy adult logic. They may not fully grasp the permanence of death, and thus, might think a simple action like giving medicine could reverse it.