单项选择题
A．20 minutes before departure B．30 minutes before departure C．45 minutes before departure D．60 minutes before departure
A．can be found in any library B．can be read directly from the Internet C．can be read by any one who has a computer D．can be read when special software is installed
A．Husband and wife． B．Nurse and patient． C．Teacher and student． D．Boss and employee．