Knowing absolutely nothing about any of these events- obviously, "C". Is the only event necessarily capable of unifying a country.
Nothing can possibly unite a country like overthrowing and kicking out foreign rulers!
A- No appointed ruler can satisfy all factions.
B- As above, so below.
D- Beside the fact that one guy arming himself is not going to make everybody happy, that he had to do it secretly implies that he must not have had all the country behind him.
