Final answer:
B. The amending process is the feature of the U.S. Constitution that enables it to be a 'living document' by allowing amendments to be made with broad support, thus letting it respond to changes over time.
Step-by-step explanation:
The feature included by the framers of the U.S. Constitution to ensure that the American government would be able to respond to future changes and act as a "living document" is B. the amending process.
This process allows the Constitution to be amended to meet the nation's needs, reflect changing times, and address unforeseen issues.
The framers learned from the rigid amendment process of the Articles of Confederation and created a more flexible system within the Constitution.
To amend the Constitution, approval is required from two-thirds of both houses of Congress and three-fourths of the states, ensuring broad support for any changes.
By this design, the Constitution is equipped with a mechanism to adapt and evolve, which has allowed for significant alterations such as the abolition of slavery, the establishment of civil rights, and changes to the electoral process amongst numerous others.
This ensures that the states have a meaningful role in any constitutional amendments and preserves the balance of power between the federal government and the states.