I have a non-functional installation of 14.04, byproduct of a failed upgrade to 16.04 and an attempt at reinstalling 14.04. This is related to
Install Ubuntu from ISO... cannot install grub
Broken 14.04 LTS while upgrading to 16.04
So now I want to reinstall 14.04, wiping the previous installs. But I want my data partition sda4 to be untouched and accesible. Is that posible? Which option should be selected from the installation menú?