The correct answer is "They recognize that she loves a human man".
Ariel and the others slyphs leave Belinda behind once they find out that she has feelings for a human male. Ariel is able to see Belinda's desire to be with this man by penetrating deep into her mind. T<u>hey are afraid that Belinda is going to lose her powers, since the slyphs will only protect her for as long as she rejects her involvement with the human race</u>, which she was no longer able to do because of her romantic feelings for a man.
