多项选择题 Given: Which two code fragments, inserted independently at line 13, will compile?（）

多项选择题 Given: Which four code fragments, inserted independently at line 7, will compile?（）

多项选择题 A company has a business application that provides its users with many different reports: receivables reports, payables reports, revenue projects, and so on. The company has just purchased some new, state-of-the-art, wireless printers, and a programmer has been assigned the task of enhancing all of the reports to use not only the companys old printers, but the new wireless printers as well. When the programmer starts looking into the application, the programmer discovers that because of the design of the application, it is necessary to make changes to each report to support the new printers. Which two design concepts most likely explain this situation?（）