Here's why:
* Period often refers to a specific point in time or a historical era. It acts as a symbol to represent that time frame and its associated events, characteristics, or cultural trends.
Let's look at why the other options aren't as fitting:
* a) proper: This refers to something that is correct or appropriate, not a characteristic of "period."
* b) moral: This deals with ethical principles, not directly related to the meaning of "period."
* c) rebellious: This suggests defiance or resistance, which isn't inherent to the term "period."
Example: The Victorian period is symbolic of a time of social change, technological advancement, and specific artistic styles.