By definition, it is important to remember that a circle has 360 degrees.
According to the information given in the exercise, you start at this point on the unit circle:
Observe the following picture:
By definition, from the point (0,-1) to the point (1,0) there are 90 degrees.
Therefore, if you move 300 degrees counterclockwise from the point (0,-1), you can subtract 90 degrees from the 300 degrees in order to calculate which angle in degrees will you end up on the unit circle:
Therefore, you will end up with 210 degrees.
The answer is: Third option.