Critical Reasoning

A chemical company claims that, since only one of
520 rats that were given high doses of a new artificial
sweetener developed cancer while all the others
remained healthy, the sweetener is not carcinogenic
for human beings and ought to be approved for
human consumption.

Which of the following, if true, most strongly
supports the chemical company’s claim?
(A) Chemicals that are carcinogenic for rats are
usually also carcinogenic for other animals, such as
guinea pigs, used in experiments.
(B) The spontaneous incidence of cancer in this
particular strain of rat is approximately one in 540.
(C) Tests conducted on a certain strain of mouse
show that, of 500 mice given a dose of sweetener
similar to that given the rats, 53 developed cancer.
(D) Certain chemicals that are carcinogenic for
human beings have been shown not to be
carcinogenic for rats.
(E) The average lifespan of the strain of rat used in
the experiment is 2 years the chemical company
terminated the experiment when the rats were 13
months old.

ans is 'b'..kindly explain

Oh this one is tough.

Conclusion: this company bases its "human consumption recommendations" on rat tests. So, its assumed that whatever happens to the rats technically happens to humans too.

A--other animals doesn't have to include humans
B--keyword here is SPONTANEOUS. 1/540 rats die for no reason. in relation to the stimulus, statistics support that that one rat had a freak death, totally unrelated to the sweetner. Thus, since the company bases its recommendations on the rats and technically, none of them died due to the sweetner, it is infact safe for humans to consume the sweetner.
C--irrelevant. we are talking about rats not mice.
D--this weakens not strenghtens.
E--irrelevant since the rats weren't around 2 yrs old anyway

Great Q indeed!!

is the option at B a typo?

one in 540?or one in 520?

freaky one bc there is no comparison with human except for assumption. In this case B - it supports sweetener's safity at least

B) The spontaneous incidence of cancer in this
particular strain of rat is approximately one in 540.
B looks good

i think option B looks good