The correct answer is option Observations can be made from outside the "system".
The study of the plate tectonics allows the observation of the movement of the plate tectonics. These observation can be study to determine the pattern of the movement from outside the plate tectonics system and the event occurring due to plate tectonics can be predicted.
Isotopes
The answer has to be 20 characters long so this is irrelevant.
A common cold i believe .
Deforestation is not a natural change.
