Question

the angle of incidence and angle of reflection are measured relative to the line.

Explanation:

In the context of reflection, the angle of incidence is the angle between the incident ray and the normal line (a line perpendicular to the reflecting surface at the point of incidence). Similarly, the angle of reflection is the angle between the reflected ray and the normal line. According to the law of reflection, the angle of incidence is equal to the angle of reflection, and both are measured with respect to the normal line.

Answer:

normal