You can pay to be upgraded to a business class seat.你可以付费升级到商务舱。Helicopters have been upgraded and modernized.直升机已经更新换代，装配了现代化设备。They upgraded the land by improving it with new buildings.他们建造新楼房来提高土地的等级....
The quarterly magazine is a periodical published every three months.季刊是每3个月出版一次的期刊.Not for circulation: newspaper, periodical, reference book, cyclopaedia , CD - ROM and video cassette recorder.不提供外借的资料: 报纸 、 杂志 、 工具书 、 ...