经济学人下载:一周要闻 众议院提交弹劾文件 以色列再次大选 美伊交换战俘

The hunt for her killer will continue, with police aided by the army and air force.
警方将在陆军和空军的帮助下，继续追踪谋杀她的凶手。 

2.step down 下台

The manager had to step down on account of poor health.
那位经理由于身体不好, 只能辞职不干。

3.run for 竞选

Each group selected candidates to run for president and vice-president.
每个组推举出候选人参加总统和副总统竞选。
 

4.public security 公共安全

The government is tightening up public security.
政府正在加强公共治安。