Repair Disk Permissions in Disk Utility

In which of the following scenarios would it be useful to run Repair Disk Permissions in Disk Utility to resolve the issue?
A. Computer fails to turn on.
B. Cannot complete a OS X Lion install.
C. Cannot install any application into /Applications.
D. Cannot open one Numbers document. Other Numbers documents open without issue.
[toggle title_open=”Close Me” title_closed=”Answer” hide=”yes” border=”yes” style=”default” excerpt_length=”0″ read_more_text=”Read More” read_less_text=”Read Less” include_excerpt_html=”no”]C[/toggle]