It's important to note that not all of the properties in the item class will necessarily exist on every Content object in that class, and that is acceptable.

一定要注意，条目类中的所有属性不一定在这个类中的每个Content对象上都存在，这是可以接受的。

youdao

The inquiry of any EMS item is acceptable within 4 months after the date of Posting; please take the third copy of this bill or the receipt to make the inquiry procedure at the mailing office.

本单第三联是交寄邮件的凭证，凭此联或收据可在自交寄邮件之日起四个月内在交寄邮局办理查询、逾期不再受理。

youdao

The inquiry of any EMS item is acceptable within 4 months after the date of Posting; please take the third copy of this bill or the receipt to make the inquiry procedure at the mailing office.

本单第三联是交寄邮件的凭证，凭此联或收据可在自交寄邮件之日起四个月内在交寄邮局办理查询、逾期不再受理。

youdao