How many degrees are in a straight angle?

A straight angle measures 180 degrees. This is defined as the angle that results when two rays extend in opposite directions from a common endpoint, essentially forming a straight line. The concept of a straight angle is fundamental in geometry, representing the maximum measure that can exist without changing direction.

In contrast, a 90-degree angle is known as a right angle, which forms a quarter turn. A full angle measures 360 degrees, representing a complete rotation, while a 270-degree angle indicates a three-quarters turn, still leaving a remaining quarter turn to complete the circle. Thus, the only option that corresponds to the definition of a straight angle is 180 degrees.