U. S. scientists studied the causes of animal hibernation. Blood was drawn from hibernating chinchillas and injected into the veins of two chinchilla legs that had been released from hibernation and placed in a 7 ° C cold room. The chinchilla went into hibernation again. In June of the same year, blood was injected from the two chinchillas into the veins of the legs of three active chinchillas. Although it was summer, the three active stages The chinchillas went into hibernation again. In July of the same year, Dong took blood from these three chinchillas and injected five active chinchilla legs into the veins. As a result, the five chinchillas also went into hibernation. Blood from the hibernating marmot was injected into the veins of the active chinchilla leg. As a result, the chinchilla also entered hibernation. Which conclusion can be drawn from this? ['It is inhumane for American scientists to disrupt the laws of animal hibernation.', 'Chinchillas have a long hibernation period.', 'During the active period, animals can be hibernated by being injected with the blood of hibernating animals.', 'Blood from marmots and chinchillas does not cause rejection.']