Which source should you NOT consult to validate an advertisement's claim?



A-- peer-reviewed scientific journals



B-- websites of government agencies



C--your doctor



D-- website of the product manufacturer



Answer :

The answer is most likely D. 

The product manufacturer will be biased. Of course they will support the claim, because they make money if you believe the claim and buy their product. 

It's better to consult the other sources, assuming of course that they are unbiased and do not have any conflicts of interest. 
I would think that no matter what the advertising is about the least objective source for truthful information would be the product website. After all, their goal is to sell a product to consumers.