an ID card
加油!不明白再问!如果帮到你,请采纳,谢谢!句子开头有没有上下文？根据句子内容可用An或The如The IDCard on the desk is his .The IDCard is Tom这句是对的。（ 特指用THE）特指用 什么情况使用一般第二次出现地名词前，或根据句意特指某个人或某样东西前（ 就如你前面所给的例子:The ID Card is Tom's .）如There is a book on the desk. The book is mine .桌上有一本书，那本书是我的。The old man over there is a doctor .那边那个老人是医生。