Which of the following was the most significant outcome of McCulloch v. Maryland?

Congress could establish branches of the National Bank in each state.
The U.S. Constitution was expanded with the addition of the Necessary and Proper Clause.
States could not tax the Federal government, but the Federal government could tax the states.
The Federal government was granted authority over a state.

The most significant outcome of McCulloch v. Maryland was the expansion of the U.S. Constitution with the addition of the Necessary and Proper Clause. This clause greatly expanded the powers of the federal government by allowing Congress to enact laws that were necessary for the execution of the powers granted by the Constitution.