4. Why can it be difficult to establish a democracy even after an oppressive government is defeated?

In simple terms, the main reason behind the fact that the abolishment of an oppressive government might not lead to democracy is the level of individuals ideological differences.

Democracy establishment is not a one man thing. Thus, there can be a number of individual who would take the opportunity to govern the nation for themselves and to not hand over the liberty to people.

the answer is a) to be able to obey them.