Assertion: echidna's ear | /r/CapableOf | begin blackening after around 40 days
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Source sentences:
text: The ear begins blackening after around 40 days, when it is less than 1 cm (0.39 in) long, and by the time the ear becomes erect, it is between 1.2 and 1.6 cm (0.47 and 0.63 in).