The correct answer is: Option C. To turn.
The root in the word covert is "vert", which is a latin word meaning "to turn". This word is the root for other terms, such as vertical, invert, revert, and convert. These all refer to the change in position or angle of something.
I.e.: Invert can be defined as the turning of something to its opposite direction, while revert can be defined as the turning of something to its original direction.
