The American President Is Often Referred to as the World's

The American president is often referred to as the world's most powerful leader.Despite this, presidents often find policymaking difficult.Why?

A) The Constitution clearly provided for legislative supremacy and failed to give the other branches enough checks and balances against it.
B) The modern consistency of divided government, where one party is in control of the White House, and another in control of one or both houses of Congress
C) The separation of powers, and checks and balances set forth in the Constitution
D) The president does not control the federal budget.