单选题：Questions are based on the following passage．Genetically mod

Questions are based on the following passage．
Genetically modified maize ( 玉米) causes cancer: that was the gist of one of themost controversial studies in recent memory, published in September 2012 by Food andChemical Toxicology. Well, actually, it doesn't. On November 28th the journal retracted ( 撤回) it. It would be too much to say that GM foods have thereby been proven safe.
But no other study has so far found significant health risks in mammals as a result ofeating them.
The article was by Gilles-Eric Seralini of the University of Caen, in France, andhis colleagues. It described what happened to rats fed with NK603 maize, a variety maderesistant to a herbicide called glyphosate ( 草甘膦 ) by a genetic modification made byMonsanto, an American firm.
In Dr. Seralini's experiment, rats fed with the modified maize were reckoned morelikely to develop tumours than those which had not been. Females were especially badlyaffected: their death rates were two or three times as high as those of control groups. (Ratsfed with diluted ( 稀释的 ) glyphosate also suffered health damage.)
The article was explosive. Jean-Marc Ayrault, France's prime minister, said thatif its results were confirmed his goverrlment would press for a Europe-wide ban onNK603 maize. Russia suspended imports of the crop. Kenya banned all GM crops. Thearticle came out two months before a referendum (公投 ) in California that would haverequired the labelling of all GM foods. It played a role in the vote, though in the eventthe proposition was defeated. The paper had all the more impact because itcontradictedprevious studies on GM foods.
But Dr. Seralini's paper was also explosive for reasons unrelated to its content.It stirred up controversy before it was even published because the authors insisted thatjournalists who were given advance copies could not seek independent comment on thecontents when writing their articles, and would face a large fine if they did so. This wasan unusual and widely criticised requirement, which had the effect of ensuring that third-party criticism of the paper did not appear during the important early days when a hugeamount of public attention was focused on the findings. That may help explain the panickyreactions in France, Kenya and Russia.
Though the paper has been retracted, that is unlikely to be end of the matter. Thejournal's publisher said there was "no evidence of fraud or intentional misrepresentation ofthe data", which are the usual justifications for retraction. Scientific opinion runs stronglyagainst the conclusion that GM foods are harmful--but not universally so.
What do we know about GM foods so far? A．They have been proven safe for people to eat.
B．They can cause cancer to some extent.
C．All of the articles about them have been retracted.
D．No other proofs of GM foods having health risks on mammals.