How many degrees are in a straight line?

A straight line measures 180 degrees. This is defined in geometry, where a straight angle is formed by two rays that point in opposite directions, creating a line. When you consider the angle formed at any point on a straight line, it represents a half-turn, which corresponds to 180 degrees.

The other choices reflect different kinds of angles or full rotations. For instance, 90 degrees is a right angle, while 360 degrees represents a complete rotation around a point. The 270 degrees would indicate a three-quarters rotation. However, the angle that precisely defines a straight line is unequivocally 180 degrees.