What do the the skin, lungs, and digestive system do when drugs enter the system?

Drugs undergo four stages within the body: absorption, distribution, metabolism, and excretion. Drugs can be absorbed through the skin.
Or, some drugs can be inhaled as gases. Gases penetrate the lining of the esophagus and lungs very quickly, which allows the drug to enter the bloodstream. 
 Once a drug has entered the bloodstream,the blood throughout the body carries the substance with it. 
The digestive system is involved in the process of metabolism of the drugs. and transform drugs into substances that can be expelled by the body. Enzymes within the liver break down the drugs.

The correct answer is a. we know this because n (hap) + n (hap) = 2n (dip).

The infrared (ir) and the ultraviolet(uv) represent the two extremities of the visible spectrum (400-700nm). while ir represents electromagnetic radiation with wavelengths longer than those of visible light, uv represents wavelengths shorter than visible light