Let's say you opened your laptop and positioned the screen so it's exactly at 90°—a right angle—from your keyboard. Now, let's say you could take the screen and push it all the way down beyond 90°, until the back of the screen is flat against your desk. It looks as if the angle disappeared, but it hasn't. What is the angle called, and what is its measurement? A. Straight angle at 180°
B. Linear angle at 90°
C. Collinear angle at 120°
D. Horizontal angle at 180°