Quaalude and Sopor are brand names for which drug?

Methaqualone is the correct answer as Quaalude and Sopor are indeed brand names associated with this particular substance. Methaqualone is a sedative and hypnotic medication that was originally used for the treatment of insomnia and as a muscle relaxant. It gained popularity in the 1970s but became notorious for its potential for misuse and addiction, leading to its eventual withdrawal from the market in many countries.

In contrast, the other choices — Diazepam, Phenobarbital, and Alprazolam — are different medications that belong to various categories of tranquilizers and benzodiazepines, each with its own specific indications and effects. Diazepam is well-known for its anxiolytic properties, phenobarbital is primarily used for seizure control, and alprazolam is commonly prescribed for anxiety and panic disorders. While these medications are all sedative in nature, they do not share the brand names identified in the question.