Hola Inma,
The sentence given was "resultados terapéuticos en el dolor de estómago, cuello, espalda y pierna." In the A2 "Everything hurts!" exercise for this week there was a sentence "También, tengo dolor de estómago y de pies," where the "de" was repeated. I rationalised this as being way of saying that I have pain from / of stomach and from / of feet. I can't understand why the "de" isn't repeated in the example above from this B1 exercise.
Can you help please
Saludos
John