Answer: D. There is a dimmer switch
Step-by-step explanation:
Dimmer switches have been known to cause radio interference especially the solid state ones. To counter this, dimmer switches usually come with a component to suppress radio interference, this doesn't work for all dimmers and the cheaper dimmers are usually more prone to this problem.
If Leticia's dining room makes use of a dimmer switch, it is the most probable reason for radio interference.