試題詳解

21. What is the reason geologists have increased their monitoring of the Long Valley Caldera?
(A) It has been more than 150 years since the last eruption.
(B) Eruptions happen frequently in volcanic chains of such size.
(C) The area is experiencing geologic activity indicative of an impending eruption.
(D) The swelling of the caldera may damage the sensitive geodetic equipment.