Why is A Incorrect?

Could some one please show how A and E differ? Thanks!

Both the passage and E commit a flaw of assuming that because the unit is the most beautiful unit as a whole, that the most beautiful individual must be in that unit. They ignore the possibility that the most beautiful one could be in an otherwise ugly area. A however, controls for this issue: it tells us that the most extreme ones in the entire area are in the most extreme unit, so the most extreme individual in the most extreme unit is in fact the tallest in the region.