Which is the BEST example of checks and balances?

ACongress may override a president's vetoing of a bill
BThe Supreme Court bases its judgments on Constitutional law
CThe president works to ensure that existing laws are enforced
DThe Constitution may be amended to fit changing circumstances

Verified Answer :

ACongress may override a president's veto. 
The idea behind checks and balances is to spread the power evenly between each government branch, (Separation of powers). While the president can veto a Congressional bill thus exercising a separation of power he may be paradoxically overrided if 2/3 of both the House and the Senate vote in favour of doing so.

Answer:

Explanation:

The answer is A