Question 1748Navigation General

The correct answer is B) Greenwich mean time. Universal Time (UT1) is another name for Greenwich Mean Time (GMT), which is the mean solar time at the prime meridian (0° longitude) located at Greenwich, UK. GMT is the standard time zone used for maritime and aviation purposes, and it is the basis for coordinating time signals and navigation worldwide. The other answer choices are incorrect: A) Atomic time is a time scale based on atomic clocks, which provide a more precise measure of time than the Earth's rotation. C) Ephemeris time is a historical time scale based on the motion of celestial bodies, which was used before the adoption of atomic time. D) Sidereal time is a time scale based on the Earth's rotation relative to the fixed stars, rather than the Sun.