OG4 阅读 Q42

Choice C is the best answer. The author explains that a "powerful volcano"erupted around 750 years ago and caused "a centuries-long cold snap known as the Little Ice Age" (lines 1-3,"About ... Ice Age"). The author then states that a group of scientists believe the volcano Samalas was this "powerful volcano," and she explains how the scientists' research supports this claim (lines 17-78,"In 2012...in 1258 C.E").
Choices A, B, and D are incorrect because they do not identify the main purpose of the passage.