题目选项分析

Unlike frogs that metamorphose from tadpoles into adults within a one-year period, mountain yellow-legged frogs of the Sierra Nevada take three to four years to reach adulthood, and so they are restricted to deeper bodies of water that do not dry up in summer or freeze solid in winter.

Unlike frogs that metamorphose from tadpoles into adults within a one-year period, mountain yellow-legged frogs of the Sierra Nevada take three to four years until they reach adulthood, thus restricted to deeper bodies of water that do not dry up in summer or freeze solid in winter.