Classical China laid the foundations for arguably the single most important civilization in the history of the planet. Any stereotypical ideas you have about the way China is from borders, language, writing, technology, empires, rulers, etc. come from this era. From the point where the region was first unified under the legalist Qin Shi Huangdi to the fall of the Han empire, what we know as China today took shape.

Western schools often overlook the importance of Han China (instead focusing on Greece and Rome). Don't fall into this trap. According to the AP, Europe cannot be more than 20% of the exam. In my opinion, China should garner your attention more than any other culture over the span of history. So... pay attention.