Because addictive drugs are phsyically harmful, their use by atheletes

Because addictive drugs are physically harmful, their use by athletes is never justified. Purists, however, claim that taking massive doses of even such nonaddictive drugs as aspirin and vitamins before competing should also be prohibited because they are unnatural.This is ridiculous; almost everything in sports is unnatural, from high-tech running shoes to padded boxing gloves to highly-specialized body building machines. Yet, none of these is prohibited on the basis of it being unnatural. Furthermore, we should be attending to far more serious problems that plague modern sports and result in unnecessary deaths and injuries. Therefore, the use of nonaddictive drugs by athletes should not be prohibited.

conclusion of the argument--the use of nonaddictive drugs by athletes should not be prohibited.

we need to find the answer choice that weakens the conclusion

let's see the answer choice

A) Massive doses of aspirin and vitamins enhance athletic performance

this answer choice strengthens the conclusion---if these drugs enhance the athlete's performance than they are helpful for athletes they should
not be prohibited--but we need an answer choice that weakens the conclusion hence, (incorrect)

B) Addictive drugs are just as unnatural as nonaddictive drugs like aspirin and vitamins

this answer choice says addictive drugs are just as unnatural as nonaddictive drugs---but we are concerned here about non-addictive drugs and why it should not be
prohibited(which will help weaken the conclusion)--knowing similarity between addictive drugs and non-addictive drugs does not effects the conclusion and does
not help weaken the conclusion hence, (incorrect)

C) Unnecessary deaths and injuries occur in other walks of life besides modern sports
we are not concerned about the deaths and injuries of other walks of life ---we are concerned about the nonaddictive drugs our conclusion is talking about
this answer choice does not talks about the nonaddictive drugs hence, has no effect on the conclusion (incorrect)

D) There would be more unnecessary deaths and injuries if it were not for running shoes, boxing gloves and bodybuilding machines

this answer choice also does not talk about why nonaddictive drugs should not be prohibited(which will help weaken the conclusion)---it talks about deaths and
injuries that would occur if running shoes, boxing gloves and bodybuilding machines were not present ---this have no effect on the conclusion
hence, (incorrect)

E) Taking massive doses of aspirin or vitamins can be physically harmful
if taking massive doses of nonaddictive drugs (aspirin or vitamins) can be physically harmful then their use is not justified and their use
should be prohibited-----this answer choice weakens our conclusion and hence, is a (correct answer)