Unable to fetch some archives, maybe run apt-get update or try with--fix-missing?

Today in Liunx to unpack the zip package, found that the system is not installed unzip package, so run sudo apt-get install unzip, but there is always no way to install, so the Internet to find reasons, and some said the source files need to be modified, so run sudo vi/etc/ Apt/sources.list View the source file, and replace the contents, found or not. Later asked colleagues, he let me ping us.archive.ubuntu.com, found Ping, and later ping the next domain name, found also ping not pass, only to find that the network is not connected. Let the teacher help me to solve the problem of network connection, network through, naturally good. An afternoon of time ah ... But also learned quite a lot of new knowledge.

Unable to fetch some archives, maybe run apt-get update or try with--fix-missing?