A one-party system

O exists in nearly all dictatorships today.

O is what the United States has today.

O creates an unstable government.

O results in democracy.

Right choice:

It exists in nearly all dictatorships today.

Explanation:

Many dictatorships find justification in some ideology; this type of dictatorship tends to be a rule of one-party system. In other undemocratic regimes, there may be an apparent multi-party system, but in practice, the ruling party of the dictator has real power and other entities are just collaborators.