1.A ferry crosses the river every hour.

1.渡船每小一次。

2.They could not cross the river owing to the flood.

2.由于洪水，他们不能。

3.Before the enemy's attack he crossed the river and alarmed the unarmed villagers.

3.在敌人进攻前, 他去向手无寸铁的村民警。

4.Therefore, the water-surface crossing with mobile flexible pipelines is often adopted and it is a first choice to cross an innavigable river.

4.软管水面穿越流具有铺设迅速,检修方便,容易掌握和使用等优点,尤于不通航流,软质机动管线临穿越流的首选方式。