17. Which of the following statements concerning the comparison between pre-industrial and post-industrial climate change,as described in the passage, is accurate?
(A) The post-industrial period experienced a much greater degree of climate change owing to greenhouse gases.
(B) The pre-industrial period experienced a much greater degree of climate change, owing to solar activity.
(C) Both periods have experienced a degree of change, but their primary causes are different.
(D) Scientists have yet to prove that climate change is linked to either sunspots or greenhouse gases.