Presence of Multiple (More Than Two)political Parties

Presence of multiple (more than two) political parties 

A) ​is the only guarantee of a truly stable democratic system.
B) ​does not occur in modern democratic political systems.
C) ​would be unconstitutional in America.
D) ​tends to split opposition to a dominant regime and help it maintain power.
E) ​has historically always caused the fairly rapid downfall of any political system that has had that characteristic.