23 Jan 2008, 23:28 (A)Chemicals that are carcinogenic for rats are usually also carcinogenic for other animals, such as guinea pigs, used in experiments. [We need to check against humans - Irrelevant](B)The spontaneous incidence of cancer in this particular strain of rat is approx one in 540.[This choice weakens the conclusion](C)Tests conducted on a certain strain of mouse show that, of 500 mice