How did the world's countries solve the problem that mean solar time varies continuously as a traveler's longitude changes?
A. They outlawed traveling long distances.
B. They offered a reward and thus helped spur the invention of clocks and watches that can change the time they keep as you change longitude.
C. An international convention adopted Coordinated Universal Time (UTC) as a single time zone for the entire world, so we can all be on the same time.
D. The world was divided into 24 time zones (with some variations), with all communities within a time zone keeping the same mean standard time.