Which observation supports the idea that light is made of particles?

Question

Light is produced by the interaction of magnetic and electric fields.
Light spreads out after passing through an opening.
Light diffracts when it hits a barrier.
Light moves in a straight path.

Answer 1

The observation that most supports the idea that light is made of particles is:

Light moves in a straight path.

This behavior aligns with the particle theory of light, as particles are typically expected to travel in straight lines unless they are influenced by an external force. The other observations relate more to wave properties of light, such as diffraction and spreading.