Its described as 2n. <span />
Answer:
We can tell that extinctions have occurred in the past by looking at fossils in layers of sediments. If the amount of fossils found match you can infer that they are the same organism and they are extinct. If you can't match up the bones with any animal today.
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The percentage that the off spring will be deaf is 75%. Two punnet squares are needed each for kkMm and Kkmm individuals. In punnet square 1, half of the genotypes are Km and km while half are Mm and kk in punnet square 2. The two punnet squares are then combined to form a final one where a quarter of the offspring are deaf.