Birds usually dodge unusual things and like green and blue objects. But when researchers injected sheep's red blood cells at 4 weeks, 9 weeks, and 14 weeks to simulate a parasite infection, The birds then began to explore new things in the environment and move closer to the little orange toys--they usually stay away from this color because it seems to be related to toxic food. The researchers speculate that these so-called personality changes will help Adult individuals explore larger areas and find more food, which in turn can compensate for the energy they lose as they fight infectious diseases. Which of the following, if true, cannot question the researchers' speculation? ['Green food does not provide energy for the little mallard.', 'Adult individuals with small mallards exploring larger areas mean more danger.', 'through long-term observation, it is found that the small green duck injected with red blood cells is more aggressive.', 'Sheep red blood cell release protein binds to the retinal cells of the little mallard and affects its color recognition.']