单项选择题
Questions 20 to 23 are based on the conversation you have just heard.
A．By marking down the unit price. B．By accepting the penalty clauses. C．By allowing more time for delivery. D．By promising better after-sales service.
A．mobile technology will be more widely used in education B．the role of technology in education cannot be overestimated C．mobile technology can upgrade professors’ teaching tool-kit D．iPhones and iPods will replace laptops sooner or later