When traveling abroad, your passport serves as your identity document.

出国旅行时，护照作为你的身份证明。

同一单元的其他句子

• The identity card contains your name, photo, and unique number.身份证包含你的姓名、照片和唯一编号。
• You must carry your identity card at all times in public.在公共场合你必须随时携带身份证。
• How did you obtain your new identity card?你是如何获得新身份证的？
• Don't lose your identity card because replacing it is difficult.不要丢失身份证，因为补办很困难。
• The police officer asked to see my identity card.警察要求查看我的身份证。