GMAT Sentence Correction (SC) | The scientists noted that rats suffering from the rare

The scientists noted that rats suffering from the rare degenerative disease had begun to die six monthsearlier, even though they had shown no signs of the disease then.

(A) earlier, even though they had shown no signs of the disease then
(B) earlier, but they were not showing no signs of the disease then
(C) earlier, no outward signs of the disease had been shown in them, however
(D) earlier without any signs of the disease shown then
(E) earlier, even though no signs of it were seen in them
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