Why do you think thr city was so hard to conquer?

The city of Constantinople was difficult to conquer because of their diligent use of ramparts and impressive city walls that protected them from invaders from outside. ... This conquest of Constantinople was a massive blow to Christendom by the Muslim Ottoman military.

Explanation:

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:

explanation: we can only guess at how our actions may be perceived in the future. doing something really big like killing lots of people, saving lots of people, affecting the lives of lots of people is a sure fire way of being remembered in historical records. we can also make a difference in the history records by being a small influence on something bigger, whether that is as a civil servant, scientist or artist.

of course you could argue that we all affect history just as tiny cogs in a   bigger machine.

if you mean how do people influence our opinions of things which have already happened, then simply by writing a book which looks at things form a different perspective and trying to convince people that this perspective is more accurate or truthful. people do it all the time i.e. richard the third was a terrible or was he? plenty would disagree, it's just that their views aren't the most widely known.n: