这个数字似乎有很多伪装，有时大一些有时又小一些，但无论它怎么变化都让人能认出它来。
This number assumes a variety of disguises, being sometimes a little larger and sometimes a little smaller than usual, but never changing so much as to be unrecognizable.
这个数字用来检出它所代表的数据块有无变化。
This single number can be used to check that particular block of data for any changes.
本周，流行病学家们要设法查清：每一个感染者会传染多少人；这个数字如何随时间和地点而变化。
This week, epidemiologists will try to find out how many people each infected person spreads the disease to, and how this figure changes with time and place.
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