Radon222 as a daughter in the decay chain of uranium is gaseous at room temperature. it is an inert or noble gas that does not interact chemically in the body. however it decays into pb210 which attaches itself to vegetation such as tobacco leaves as a solid and subsequently decays into po210 which emits an energetic alpha particle with 5.3 mev of energy. the inhalation of these two isotopes in the particulate matter of cigarette-smoke delivers to the average smoker a radiation effective-dose or dose-equivalent of 8 rems (radiation equivalent man) per year to the basal cells of the bronchial tissue. the "cancer dose" is the total radiation dose that if spread through a population would cause one additional cancer death and is considered to be approximately 2,000 rems. calculate the ensuing radiological risk in units of cancer deaths per year in a population of one million smokers.

4,000 cancer deaths

Explanation:

One smoker usually receives radiation dose of 8 rems (radiation equivalent man)/year to his branchial tissue cells.   Cancer dose (total radiation dose that if spread through a population would cause one additional cancer death) = 2,000 rems  

1 Smoker                 < 8 rems

1,000000 smokers <  X  rems

X = 8,000000 rems  

If cancer dose implies 2,000 rems, that would cause one additional cancer, we’ll have that 4,000 additional cancer deaths will reach that population of a million people/year. This means the 0.4 % of the smoker population

it's c (engineer's do their work with mechanical stuff not on any living being)

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.