To decrease the force that the permanent magnet applies on the electromagnet, Alice should choose an option that reduces the interaction between the two magnets.
Let's analyze the options:
A. Decrease the number of turns in the electromagnet's coil: This would decrease the magnetic field strength of the electromagnet, potentially reducing its interaction with the permanent magnet, but it doesn't directly affect the force applied by the permanent magnet itself.
B. Increase the electric current running through the electromagnet: Increasing the current would increase the magnetic field strength of the electromagnet, which would increase its interaction with the permanent magnet.
C. Decrease the distance between the magnet's poles and the electromagnet: Reducing the distance would increase the magnetic force due to the inverse square law of magnetism, thus increasing the force from the permanent magnet.
D. Replace the magnet with a stronger magnet: This would increase the force applied by the permanent magnet, not decrease it.
Among these options, the one that most directly affects the force exerted by the permanent magnet is:
A. decrease the number of turns in the electromagnet's coil.
However, it would still not appropriately decrease the force applied by the permanent magnet itself, as it is the strength of the permanent magnet that primarily determines the magnetic force acting on the electromagnet.
Given the context of the question, the correct response that might effectively reduce the electromagnet's interaction with the permanent magnet may not be fully represented.
For a definitive answer regarding decreasing the force from the permanent magnet, typically you might consider not just the electromagnet's modifications, but also changing the permanent magnet itself, which isn't listed as an independent option here. Thus, A remains the best choice from what's given.