Class c is a category of drugs. For example, All drugs that have less physical and mental effects on the human body then a class B or class A drug is a class C drug. The higher in class the drug is, when caught handling results in different amounts of punishment. Heroin is a Class A drug, and results in heavy punishment when one is caught handling it.
Officer: Your under arrest for the suspicion of handling a class c drug, anything you will and may say will be used as evidence against you in the court of law.
to days later
Judge Judy: Because you where handling a class c drug, you have 3 years punishment (Handling Class B or A is longer, nearly double the years in prison).