四、閱讀測驗(31~50 題) Questions 31~33
Ice ages, those periods when ice covered extensive areas of the Earth, are known to have
occurred at least six times. Past ice ages can be recognized from rock strata that show evidence of
foreign materials deposited by moving walls of ice or melting glaciers. Ice ages can also be
recognized from land formations that have been produced from moving walls of ice, such as
U-shaped valleys, sculptured landscapes, and polished rock faces.
【題組】33. According to the passage, what in the rock strata is a clue to geologists of a past ice age?
(A) Ice
(B) Melting glaciers
(C) U-shaped valleys
(D) Substances from other areas