The correct answer is: C. 180° east or westward.
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth’s surface. It is measured as the angle between the Prime Meridian and the point, in degrees east or west. The Prime Meridian is the line of longitude that passes through Greenwich, England. Longitudes are measured from 0° to 180° east or west.
Option A is incorrect because longitudes are measured from 0° to 180°, not 180°.
Option B is incorrect because longitudes are measured from 0° to 180°, not 180°.
Option D is incorrect because longitudes are measured from 0° to 180°, not 360°.