The graph shows the relative risk of lung cancer, according to the years of smoking and the number of cigarettes smoked each day. The following statements were made. 1 The relative risk of lung cancer depends on the number of cigarettes smoked each day. 2 The relative risk of lung cancer depends on the number of years of smoking. 3 The relative risk of lung cancer depends on the tar content of the cigarettes smoked. Which statements are supported by the data in the graph?

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