Ubuntuでpython-pipをインストール中にエラーが発生しました。

走っている間

sudo apt-get install python-pip

次のエラーメッセージが表示されます。問題の原因と解決策は何ですか？助けてくれてありがとう。

Err http://us.archive.ubuntu.com/ubuntu/ trusty-updates/main dpkg-dev all 1.17.5ubuntu5.3
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/main build-essential i386 11.6ubuntu6
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/main libfakeroot i386 1.20-3ubuntu2
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/main fakeroot i386 1.20-3ubuntu2
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/main libalgorithm-diff-perl all 1.19.02-3
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/main libalgorithm-diff-xs-perl i386 0.04-2build4
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/main libalgorithm-merge-perl all 0.08-2
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/universe python-colorama all 0.2.5-0.1ubuntu1
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/universe python-distlib all 0.1.8-1
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/main python-html5lib all 0.999-2
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/main python-urllib3 all 1.7.1-1build1
  Could not resolve 'us.archive.ubuntu.com'
Err http://us.archive.ubuntu.com/ubuntu/ trusty/universe python-pip all 1.5.4-1
  Could not resolve 'us.archive.ubuntu.com'
Err http://security.ubuntu.com/ubuntu/ trusty-security/main dpkg-dev all 1.17.5ubuntu5.3
  Could not resolve 'security.ubuntu.com'
Err http://security.ubuntu.com/ubuntu/ trusty-security/main python-requests all 2.2.1-1ubuntu0.1
  Could not resolve 'security.ubuntu.com'
E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/d/dpkg/dpkg-dev_1.17.5ubuntu5.3_all.deb  Could not resolve 'security.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/b/build-essential/build-essential_11.6ubuntu6_i386.deb  Could not resolve 'us.archive.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/f/fakeroot/libfakeroot_1.20-3ubuntu2_i386.deb  Could not resolve 'us.archive.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/f/fakeroot/fakeroot_1.20-3ubuntu2_i386.deb  Could not resolve 'us.archive.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/liba/libalgorithm-diff-perl/libalgorithm-diff-perl_1.19.02-3_all.deb  Could not resolve 'us.archive.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/liba/libalgorithm-diff-xs-perl/libalgorithm-diff-xs-perl_0.04-2build4_i386.deb  Could not resolve 'us.archive.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/liba/libalgorithm-merge-perl/libalgorithm-merge-perl_0.08-2_all.deb  Could not resolve 'us.archive.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/universe/p/python-colorama/python-colorama_0.2.5-0.1ubuntu1_all.deb  Could not resolve 'us.archive.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/universe/d/distlib/python-distlib_0.1.8-1_all.deb  Could not resolve 'us.archive.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/h/html5lib/python-html5lib_0.999-2_all.deb  Could not resolve 'us.archive.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/p/python-urllib3/python-urllib3_1.7.1-1build1_all.deb  Could not resolve 'us.archive.ubuntu.com'

E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/r/requests/python-requests_2.2.1-1ubuntu0.1_all.deb  Could not resolve 'security.ubuntu.com'

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/universe/p/python-pip/python-pip_1.5.4-1_all.deb  Could not resolve 'us.archive.ubuntu.com'

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