Final answer:
When using longitude to define positions on Earth, we start counting from the Prime Meridian (Option C), which is defined as 0° longitude and runs through Greenwich, England. Both the North and South Poles and the Equator are not starting points for counting longitude. Therefore, the correct options for starting points in counting longitude are: Prime Meridian (Option C)
Step-by-step explanation:
When using longitude to define positions on Earth, we start counting from the Prime Meridian (Option C). The Prime Meridian is the line of longitude defined as 0° and it runs through the Royal Observatory in Greenwich, England. We count longitude in degrees east and west from this meridian up to 180° in both directions, thus defining the Eastern and Western Hemispheres. The North Pole and South Pole are reference points for latitude, each located at 90° north and south, respectively. However, they are not starting points for counting longitude. The Equator, while significant for latitude measurement as the 0° latitude line, does not serve as a starting point for counting longitude either.
All lines of longitude, or meridians, converge at the poles and are equidistant at the equator, forming a circular grid around the Earth. As such, every place on Earth is situated on a meridian, which helps specify its east-west position by counting the degrees from the Prime Meridian. It's important to note that longitude is what sailors historically have used along with accurate clocks to determine their east-west position while at sea. Therefore, the correct options for starting points in counting longitude are: Prime Meridian (Option C)