The crowd fell back when the police arrived.警察到达后，人群就向后退了。

The guerrillas fell back across the border after a brief battle with the army.游击队和军队短暂交火后就撤回到边境线的另一边。

When her health insurance was canceled she had nothing to fall back on.她的健康保险被取消后，她就无所依靠了。

They had to fall back on their emergency supplies when the snow storm blocked the road to town.暴风雪封住了通往小镇的道路，他们只得依靠应急储备。