During photosynthesis, sunlight shining on a plant is absorbed. Through several chemicals reactions, the plant produces sugar, high-energy compound, from simpler substances.

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.

you need to stop taking that class

the answer your looking for is c).