A drug inspector enforces the law in the field, a chemical examiner and a government analyst both test specific samples referred to them, but none of these three heads the laboratory itself. The officer who is actually in overall administrative charge of a state's drugs testing laboratory, overseeing its staff, standards, and licensing functions, is the drugs controller. So the answer is drugs controller.
A quick way to settle this is to ask: which of these four titles describes a "head of department" role rather than a technical/testing role?
Only the drugs controller occupies the "in charge of" position described in the question; the other three are technical or enforcement staff who work under that authority.
Therefore, the correct answer is Drugs controller.