Final answer:
The prime meridian, defined as 0° longitude, ran through Greenwich, England before 1884, and was officially adopted at the International Meridian Conference that year.
Step-by-step explanation:
The prime meridian prior to the year 1884 indeed passed through Greenwich, England. However, the options provided can be a bit misleading if not examined carefully. The prime meridian was at 0° longitude and passed through Greenwich as these ideas are interconnected. But it was not subject to frequent changes nor was it established at the International Meridian Conference.
It was already in popular use due to the location of the Royal Observatory in Greenwich which played a significant role in the history of astronomy and navigation, before being officially adopted at the conference in 1884. Longitudes are measured from the prime meridian, which is defined as 0°, up to 180° east or west. This method of defining longitude helped simplify global navigation and standardize timekeeping.