Option 1: General Meridian Time - This option is incorrect. The correct term is Greenwich Mean Time (GMT), not General Meridian Time.
Option 2: Greenwich Mean Time - This option is the correct answer. GMT refers to the mean solar time at the Royal Observatory in Greenwich, London. It is the standard time used as a reference point for timekeeping in various regions across the globe.
Option 3: Global Mean Time - This option is incorrect. The correct term is Greenwich Mean Time (GMT), not Global Mean Time.
Option 4: None of these - This option is incorrect. The correct answer is Option 2, Greenwich Mean Time (GMT).
In conclusion, GMT stands for Greenwich Mean Time, which is the standard time used as a reference point in various regions worldwide.