Which is an unreliable source?

A scientist who studies dinosaurs presents her research on velociraptors at a science convention.
An advertisement for acne medication claims it can clear up acne in less than one week.
An article on the Centers for Disease Control and Prevention (CDC) website discusses the salmonella bacteria.
A chemistry teacher discusses possible projects for the upcoming science fair.

An advertisement for acne medication claiming it can clear up acne in less than one week is an unreliable source.