Final answer:
Without the specific sentence provided, it's impossible to determine the subject of sentence 1. The information given is related to geographical coordinates, including the North Pole and the Greenwich Meridian.
Step-by-step explanation:
The student is asked to identify the subject of the first sentence given a choice of four options. However, the information provided is about geographical concepts such as lines of latitude, the poles, and lines of longitude, particularly focusing on the North Pole and the Greenwich Meridian. Since the specific sentence in question is not included in the information provided, it is not possible to accurately determine the subject of sentence 1. This question seems to be related to understanding geographical coordinates and the significance of certain lines of latitude and longitude in navigation and Earth sciences.