Please help with this

4

Explanation:

Light refracts when it passes through something transparent at an angle so that eliminates the other 3.

or put differently

Light refracts whenever it travels at an angle into a substance with a different refractive index (optical density)

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.