原题
录音 1
Why does the speaker mention "inferred volcanic seismic activity"?
ATo imply that earthquakes cause upsweep
BTo clarify why more data about upsweep is needed
CTo suggest that one theory about upsweep is wrong
DTo explain a possible origin of upsweep
正确答案：D
解题思路
老师暂未填写解题思路。