Answer: It is a 90 Clockwise Degree Turn.
Explanation:
From my knowledge, a 90-degree turn is a turn to the right.
So if you turn the "C" in the Y-axis 90 degrees you will get The "C" on the X-axis.
For Example: When you walk around a street you either turn 90 degree's to the right or 90-degrees to the left.
Hope this Helps!