Which of the following corresponds to 0 on the Beaufort scale?

The Beaufort scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale.

The numbers 0 to 12 were introduced by Admiral Sir Francis Beaufort in 1806, 0 referring to a calm and force 12 to a wind of hurricane force, while serving on HMS "Woolwich". The scale was made a standard for ship's log entries on Royal Navy vessels in the late 1830s and was adapted to non-naval use from the 1850s. In 1853, the Beaufort scale was accepted as generally applicable at the First International Meteorological Conference in Brussels.

In 1916, to accommodate the growth of steam power, the descriptions were changed to how the sea, not the sails, behaved and extended to land observations. Rotations to scale numbers were standardized only in 1923.

Nowadays, meteorologists typically express wind speed in kilometres or miles per hour or, for maritime and aviation purposes, knots; but Beaufort scale terminology is still sometimes used in weather forecasts for shipping and the severe weather warnings given to the public.