Answer:
A. North and South poles
B. Longitudes are measured from zero to 180° east and 180° west (or –180°), and both 180-degree longitudes share the same line, in the middle of the Pacific Ocean
C. These lines are also known as meridians
D. The 0-degree line of longitude that passes through the Royal Observatory in Greenwich, England is the Greenwich Meridian. It's also called the Prime Meridian
