Sophie said that the part in question does not belong to an animal. This therefore invalidates options B and C as only animals would have lungs or legs.
Sophie then says that the part does not grow in the direction of light so that removes stems as the correct option because stems grow towards light in order to allow leaves to carry out photosynthesis.
Roots on the other hand grow towards gravity so they grow away from light which means that the correct answer is roots.
