No :) In his book "What is History?", the well-known British historian Edward Carr points out a fundamental difference between archaeologists and historians. Archaeologists are concerned more with accurate facts--ideally, all professional archaeologists with perfect technology trying to figure out how old an ancient coin is or where it came from will give us the same answer. Historians are also concerned with accurate facts, but their primary purpose is to decide which facts are historically significant and why. To give you a recent example, I believe all professional historians will agree that Imperial Japan invaded China in 1937, and Nazi Germany invaded Poland in 1939. Those are facts and anyone who says otherwise will be discredited. However, there is no 100% consensus on which invasion should be considered as having started WW2, although most would say 1939. An Oxford professor, Rana Mitter, was recently interviewed on my local news channel as he argued that WW2 started in 1937. Neither side is wrong, they are simply offering different interpretations of the same facts.

Of course, there is also the fact that many people have their own biases, agendas, etc. and may want to present history in a certain way for their own purposes.

A final reason you can consider is that different facts surface at different times, which means historical perspectives change over time as well. A good example is when the closely guarded Soviet archives was finally opened in 1991 after the collapse of the USSR. That led many historians, particularly in the US and UK, to change their minds about whether the US or USSR was more responsible for escalating the Cold War, since now they could view the Soviet side of the story as well.

You've actually touched on some very complex ideas relating to historiography (the theory of history). If you are interested, I highly recommend the book "The Landscape of History" by John Lewis Gaddis. I personally found it a very accessible read that discussed many key concepts of historical practice.

I am not a professional historian, just an enthusiast! So if I have made any mistakes, please correct me. :)

Edit: The reason why different versions may not be awarded the same marks in exams is because a lot of testing like the GCE A Levels (which I took) is standardised and so there is often some kind of guideline to follow, so huge numbers of students (often from all over the world) can be graded fairly on similar criteria. I'm not sure but I think at higher levels e.g. college people are more willing to consider alternative views if they are well-argued and substantiated.

Historians seek to create narratives and interpretations about the past. They use evidence to do so, of many different kinds. But good historians know that the question of how to interpret the evidence, which evidence to privilege over other, contradictory evidence, and how to string that evidence into an interpretive narrative, is a very individual activity that will depend on the judgment of the individual historian.

Which is to say, on many topics there are different interpretations. Each interpretation may privilege different forms of evidence, or interpret the same evidence differently. It is not a question of "objective" versus "subjective" (these same forces play out in other forms of knowledge-making), but the history is much more complex than, say, particle physics (though it often doesn't appear to be the case!) in terms of how the evidence may or may not give you a straightforward answer (and indeed, some answers may simply be inaccessible to us). Even "stating the facts" is not as easy as some of the other respondents appear to think — what is or is not a fact, and how to make sense of said fact, can be a tricky question in and of itself. (Historians spend a lot of time getting the history behind any individual piece of evidence — what we call "contextualizing" it — because even making sense of the evidence requires research and interpretation. It is never as simple as just pointing to a document and saying, "well, here's the truth!")

Historians may not believe that there is "one interpretation to rule them all," in part because interpretations are embedded in their own historical context (that is, even when we look at the past, we cannot escape the fact that we are looking as people in the present), but there are interpretations that are stronger or weaker than others, narratives that are "more true" than others, even if no single narrative is likely to be privileged as "the final story."

If you are confronted with two very radically different claims, the best way to approach it is to characterize them as different claims. See for example how I describe the "orthodox" and "revisionist" interpretations of the "decision to use the atomic bomb" in this recent thread. While I do express a preference (I think neither are correct), I do make an effort to characterize what the various arguments are for either interpretation, and attribute the various interpretations to the historians or historical actors who have created them. For historical interpretations of a very large scale (e.g., why did the industrial revolution occur? why did World War I start? why didn't China have a Scientific Revolution?) there are unlikely to be single, simple answers and there often are competing interpretations.

As for your exam, you will need to ask your instructor. In theory a good historical exam question will allow you to acknowledge different interpretations, e.g., if the question was, "why was the atomic bomb dropped on Japan?" you would not necessarily be required to give a single answer, but could say, "some historians have claimed X, while others have claimed Y," and explain the various merits of the two views.

But if you are talking about high school history, your teacher may not even be aware of conflicting interpretations, so that might not be valuable to you. History education at the lower levels is unfortunately often a matter of rote memorization, without an acknowledgment of the role of interpretation. If your concern is your grade, as opposed to a deeper understanding of history, then you should do what your teacher tells you to do.