C:You may send the urgent letter by registered express airmail, 这封急信,你可以寄航空挂号快信, the other letters by air mail. 其他信件用航空信寄发。 B:How long will it take to send a letter to Los Angeles by registered express airmail? 用航空挂号信寄往洛杉矶要几天才能到达? C:It will take five days or so. 大约五天左右。 B:If I send it by ordinary mail, how long will it take? 如果我用普通信件邮寄,要花多久? C:About a half month or so. 大约半月左右。 B:Then, I'll send it by registered express airmail. 那么我就寄航空挂号信吧。