Heroin, commonly called as smack is a/an :

Opioid

The correct answer is Option (2)-Opioid

The drugs, which are commonly abused are opioids, cannabinoids and coca alkaloids. Majority of these are obtained from flowering plants. Some are obtained from fungi.

Opioids are the drugs, which bind to specific opioid receptors present in our central nervous system and gastrointestinal tract. Heroin, commonly called smack is chemically diacetylmorphine which is a white, odourless, bitter crystalline compound.

This is obtained by acetylation of morphine, which is extracted from the latex of poppy plant Papaver somniferum . Generally taken by snorting and injection, heroin is a depressant and slows down body functions.