Identifying parts of a mirror diagram

a horizontal line labeled b has an arrow labeled a strike it from right and above and then another arrow d emerges from the strike point at the same angle as a. a dotted line c evenly divides the angle between a and d.

in the mirror diagram shown,

which is the normal?

a

b

c , c as in the correct answer

d

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.