一旦发生紧急情况打电话给警察的英文

in case of urgency call the police

• 一旦:    in a single day; i ...
• 发生:    happen; occur; tak ...
• 紧急情况:    critical situation ...
• 打电话:    make a phone call; ...
• 给:    supply; provide
• 警察:    police; policeman