【简答题】Business Invitation Business invitations can be informal or formal. Although formal invitations are usually sent through the mail, informal invitations via e-mail and phone invitations are becoming mo...
【单选题】根据下列材料,请回答题 Please Fasten Your Seatbelts Severe turbulence (潮流 can kill aircraft passengers. Now, in test flights over the Rocky Mountains, NASA (美国航空航天局)engineers have successfully detected clear-air...