Explanation:

- The Primary Sector involves the extraction and harvesting of natural resources. Examples include agriculture, mining, and fishing.

- The Secondary Sector focuses on manufacturing and processing activities. This sector turns raw materials into finished goods, such as factories producing cars or clothing.

- The Tertiary Sector is also known as the service sector. It includes industries that provide services rather than products, like retail, healthcare, education, and financial services. This is where the service sector fits.

- Option 4, None, implies that the service sector does not fit into any of the above sectors, which is incorrect.