TOEFL Listening: TPO-TOEFL阅读TPO - A23A4R62KDGO8R35N$

Why does the author include the information that in 1997-1998 "Snowstorms in the northeast portion of the United States were more frequent and intense than in most years"? A. To provide evidence supporting the claim that El Niños are getting stronger B. To explain why the southern United States experienced copious and damaging rainfall in 1997-1998 C. To show that traditional methods are not adequate for documenting the effects of El Niños D. To identify a consequence of the fact that El Niños are now occurring a little over once every two years