Hi there! Your answer will be 45 Degrees,
This is because when the top line is facing C in this case and the bottom line is facing B it would be a 90° angle. Due to it being less than 90°, and it can not be a decimal your only choice would be 45°.
The only reason it is not 180° is because when 180° is shown it will go from A to B and show a straight line.
I hope this helped!
