The correct answer is: C. By subtracting the sum of their longitudes exceeding 180° from 360° if places are in different hemispheres.
The longitude of a place is its angular distance east or west of the Prime Meridian, which passes through Greenwich, England. The Prime Meridian is the 0° longitude line, and all other longitude lines are measured east or west of it. The longitude lines are spaced evenly around the Earth, with each degree of longitude equal to 60 nautical miles or 111.11 kilometers.
If two places are in the same hemisphere, their longitudes can be subtracted directly to find the difference between them. For example, the longitude of New York City is 74°W, and the longitude of Los Angeles is 118°W. The difference between these two longitudes is 44°W.
However, if two places are in different hemispheres, their longitudes must be treated differently. The longitude of a place in the Western Hemisphere is greater than 180°, while the longitude of a place in the Eastern Hemisphere is less than 180°. Therefore, if you subtract the longitudes of two places in different hemispheres, you will get a negative number. To find the correct difference, you must subtract the sum of the longitudes from 360°. For example, the longitude of Tokyo is 139°E, and the longitude of Los Angeles is 118°W. The sum of these two longitudes is 357°. Subtracting 357° from 360° gives us 3°. Therefore, the difference between the longitudes of Tokyo and Los Angeles is 3°E.
In conclusion, the difference between the longitudes of two places is obtained by subtracting their longitudes if places are in the same hemisphere, or by subtracting the sum of their longitudes exceeding 180° from 360° if places are in different hemispheres.