What is approximately the size of a zettabyte in terms of terabytes?

A zettabyte is equivalent to approximately 1 billion terabytes. The prefix "zetta" represents (10^{21}), and "tera" represents (10^{12}). When converting zettabytes to terabytes, you divide (10^{21}) by (10^{12}), which results in (10^{9}). This means that one zettabyte is 1 billion terabytes, making the choice of 1 billion the correct answer. Understanding these prefixes helps in grasping the vastness of data sizes in digital contexts.