and the mother has led her cubs a mile from the den. 母熊已经带领幼熊离巢1英里远

56. The sea ice still holds firm,
    海面上的冰层依然坚固
57. but it won't last much longer.
    但是这种情况不会持续太久
58. Day 10,
    第10天
59. and the mother has led her cubs a mile from the den.
    母熊已经带领幼熊离巢1英里远
60. It's time to put them to the test.
    现在该是考验它们的时候了
61. They've grown enormously in confidence,
    它们的信心日益膨胀
62. but they don't have their mother's sense of urgency.
    不过它们并不像母熊那样着急

来自《行星地球 第一季 第一集 Planet Earth S01E01 从北极到南极》第 59 行