There may be narrow passages or other choke points that too many people try to use at once .

可能会有许多人试图同时使用的狭窄通道或其它梗阻点。

We 've grown more adept at shaping these underground shelters and passages over the millennia , and today we dig for hundreds of reasons .

经过几千年，今天我们能熟练的塑造这些地下避难所或者通道，同时我们有更多的数以百计理由来建造他们。

Does spitting , as some suggest , help clear the airways and keep those crucial passages to the lungs free ?

不也有建议说吐痰其实可以帮助清理呼吸道，保持那些通向肺部的重要通道畅通么？

The length of its underwater passages is more than 4600 m while its dry part is 300 m long .

水下通道的4600多米长，干燥的部分长300米。

And the vanishing ice has begun to allow a trickle of shipping across the arctic 's generally frozen north-west and north-east passages , thus linking the atlantic and pacific oceans .

消失的冰面也开始允许船只缓慢通过通常封冻的北极西北和东北通道，从而连接了大西洋和太平洋。