This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Toxicology - 1, Subject name: Forensic Medicine
By which route of administration , least onset of action will be produced from the given options ? 
Select and explain. 
A. Application to a serous surface, B. Inhalation of gaseous form, C. Application to a bronchotracheal mucous membrane, D. Injection into blood vessels
C: Application to a bronchotracheal mucous membrane
Answer: C: Application to a bronchotracheal mucous membrane 
Explanation: Routes of Administration: In order of rapidity of action: (1) Inhaled in gaseous or vapourous form. It usually involves a volatile substance, gas, dust, smoke or aerosol. (2) Injection into blood vessels. (3) Intramuscular, subcutaneous and intradermal injection. (4) Application to a wound. (5) Application to a serous surface. (6) Application to a bronchotracheal mucous membrane. (7) Introduction into stomach. (8) Introduction into the natural orifices, e.g. rectum, vagina, urethra, etc. Some drugs can be given by rectal route to produce a systemic effect, e.g., aspirin, barbiturates, chloral hydrate, chlorpromazine, etc. (9) Application to unbroken skin. Organic phosphates, nicotine, some organic solvents and lewisite gas can penetrate the skin and produce intoxication and death .