Why Is There the Potential for Conflict Over Virtually All

Why is there the potential for conflict over virtually all aspects of government?

A) National legislatures choose the chief executives, so the unified parties need to be in control.
B) All constitutional powers are shared.
C) There is always a divided government.
D) Parties have been ideologically incohesive since the mid-1990s.
E) There are no checks and balances between the executive and legislative branches of government.