Why Is Commercial Speech Not Entitled to Full First Amendment

Why is commercial speech not entitled to full First Amendment protection?

A) Regulating commercial speech protects gullible consumers from rampant overspending.
B) Commercial entities have a history of making reliable advertising claims, and the Supreme Court wanted that to continue.
C) Commercial speech is not political speech, so it can be regulated more heavily.
D) It is difficult to determine who actually speaks for a commercial entity.