Unit of measurement of cloud cover

Answer: Option A

The unit of measurement of cloud cover is Octa. It is a unit of measurement used to describe the amount of cloud cover at any given location such as a weather station.
Sky conditions are estimated in terms of how many eighths of the sky are covered in clouds, ranging from 0 oktas.
In addition, in the SYNOP code, there is an extra cloud cover indicator '9' indicating that the sky is obscured, which may be due to fog or heavy snow.