A computer sales department promises to customers: "Computers sold by this department will be replaced within one month, repaired free of charge within one year, and onsite service will be free of labor charges within three years, except for failures caused by improper use. Which of the following is the service that the sales department should provide? (). ['Someone bought a computer, and after three months, the floppy drive had a problem and asked the sales department to repair it, and the sales department replaced the floppy drive for free.', 'The computer lab purchased 30 computers from the sales department and unpacked them after 50 days. During the installation, it was found that one of the monitors could not display color and required replacement.', "A school purchased 10 computers. Within a month, three of the computer's mice were lost, and the sales department had to make up for them free of charge.", 'Someone bought a computer and the keyboard failed after one year and asked the sales department to replace it with a new keyboard at half price.']