Answer:
A. A theme can apply in many different times, but a period applies to
one specific time span.
Step-by-step explanation:
A theme in history is commonly interpreted as a "re-occurring theme", in which it suggests that the causes as well as, in most cases, the effects would be relatively in the same area. For example, a theme in history, is that empires will always fall, and a new one will take it's place. Where is this found in history? We can trace it throughout history and show that influences that have played major roles in their respective geographical areas have generally fallen out of favor, and lose their influence. A common example can be the sphere of influence in the Middle East, in which history generally trace the influence starting from the Hittites, to the Israelites, a combined sphere of influence of Assyria and Egypt, to Egypt and Babylon, in which is followed by Persia, a return influence of Israel, and then following a long history of Roman reign, etc.etc. This also follows closely in other places, especially where Roman influence have gone (stretching from Minor Asia, Africa, Northern Europe, all the way to present-day Great Britain. This theme of spheres of influence by ruling parties transform and influence conquered people groups in shaping their economical status (connecting them with previously unknown or unfriendly tribes), their political status (having a puppet state at best, and under the influence of the conqueror), as well as their social and religious status (in which "more developed countries" were closely secured but given larger freedoms, while many times conquered groups were forced to give up their religions in turn for the conqueror's religion. Spheres of influence continued even into the modern era. Examples can be found under the US presidency's James Monroe and others, who used the U.S.'s new found economical, military, and social status to impose it's common beliefs on other nations, as well as extract natural and other "needed" resources, as well as instilling a pro-parent country influence to the area. Again, as you can see, like Rome, the US followed a policy of globalization (to a degree, as the Romans followed it to their "known-world", and the US followed it following the end of the "Doctrine of Isolation".
Remember, a theme can be described as a idea that would then extract context and examples from different parts of history that would benefit and make the theme claim true. A period, on the other hand, is a general but connected term of events that could be used to back up a theme (or disclaim one), but generally have more than one theme into it. Returning to the Roman example, we can say the theme is that the Roman's were conquerors, and back up with different time periods of Rome's legacy in fighting and conquering other people groups, but the Empire of Rome was much more than that. Their period shows their technological advances in building of roads, monuments, aqueducts, and many other wonders that continue to influence our monumental building projects, as well as a governmental structure that influences even today's governments, such as the U.S. We see themes of Ancient Rome, Ancient Greece, and even Christianity influence our founding fathers when they created the United States, and this is a classic example of a theme that has worked.
Periods and Themes work hand in hand, and to put in perspective, periods of history complement the theme that is taught.
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