試題詳解

23. It can be inferred from the passage that Mammoth Mountain ______.
(A) erupted most recently around 600 years ago
(B) is an active volcano that the USGS is monitoring for early signs of eruption 
(C) shows signs that the larger volcanic system to which it belongs is still active
(D) was formed 760,000 years ago by pyroclastic flows from a volcanic eruption