Question

how does light travel?
a light travels in straight lines only.
b light travels like a river, wherever there is an open path.
c light travels in unpredictable ways.
d it depends; if the light is bright enough it can change direction.

Explanation:

In the field of Physics (a subfield of Natural Science), the fundamental property of light propagation is that light travels in straight lines (in a homogeneous medium, ignoring effects like diffraction for basic understanding). Option A states this, while B (comparing to a river is incorrect), C (unpredictable is wrong), and D (brightness doesn't change direction; direction change is due to reflection/refraction, not brightness) are incorrect.

Answer:

A. Light travels in straight lines only.