（1） The determination of the path of Mars's orbit in 1609 became the unifying link among the two formerly separate realms of physics and astronomy.
(答案) C among改为between
（2） The Carlsbad caverns, located in New Mexico, rank between the largest underground labyrinths in the world.
(答案) B between改为among。表示多数概念，或范围时应用among。
（3） For a long time cotton ranked first bctween Alabama's crops, but today it accounts for only a fraction of the agricultural production.
(答案) A between改为among。表示范围时应用among。