The development of farming changed the lives of some ancient Americans by

option d is correct. corroborated sources of historical evidence   is necessary to validate a claim about an event in history.

historians tend to use written sources, but audio and visual materials as well as artifacts are important objects that supply information to modern historians.

historical sources are usually divided into two categories: primary and secondary sources. depending on the historian's intent, some sources shift their designation. determining what type of sources toimplement, and the level of credibility and reliability of those sources, is a significant step in critical thinking for the historian.

explanation:

in the united states, the president is controlled by the

constitution, and in all respects subordinate to it. insofar

as it deals with presidential power, however, the american

constitution has proved to be a highly malleable document.

with very few exceptions,' the constitutional provisions relating to the president have not been changed at all since

they were ratified in 1787. but in the late twentieth century, those provisions do not mean what they meant in

1787. the constitution is a legal document, and it is enforced judicially; but its meaning was hardly fixed when it

was ratified. in particular, the contemporary president has

far broader powers than the original constitution contemplated. it is remarkable but true that large-scale changes in

the authority of the president have been brought about

without changes in the constitutional text, but nevertheless

without significant illegality.

this is a paradox. is it not clear that constitutional

changes, if not textual, are illegal? the paradox has considerable relevance to our current thinking about the presidency in particular and about constitutionalism in general.

perhaps the framers of the american constitution feared

legislative power most of all; 2 but from well-known events

in the twentieth century, it is possible to conclude that it is

presidential power that holds out the greatest risks to both

liberty and democracy. the president is by far the most visible leader in the nation; he is often the only person in government with a national constituency. moreover, he is