An organic compound that contains only carbon and hydrogen and a triple bond (all the other bonds are single bonds) is classified as: a. alkane
b. alkene
c. alkyne
d. arene

c. alkyne.

Explanation:

Hello there!

In this case, according to the attached file, it turns out possible for us to say that alkanes have only single-bonded carbon atoms, alkenes have two double-bonded carbon atoms and alkynes have two triple-bonded carbon atoms.

In such a way, according to the aforementioned definition, we infer that that an organic compound that contains only carbon and hydrogen and a triple bond (all the other bonds are single bonds) is classified as c. alkyne.

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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.