The ratio of Carbon, Hydrogen, and Oxygen are 1:2:1 in carbohydrates
A dog and a tick would have a parasitic relationship. Seeing as how, if anything, the tick is harming the dog and the dog isn't getting anything in return, but the tick is getting both a food supply and a host, their relationship would be classified as parasitic.
The risk of lung cancer death is no different between medium, low, and very low-tar cigarettes.
People who smoke low-tar cigarettes compensate the lack of tar by changing their breathing habits, for example, they will take deeper drags or hold the smoke in for a longer period of time, basically negating the supposed " low-tar" effect.