(2) Obviously not. When both D and E are midpoint, quadrilateral is obviously a square.

(3) Let CD=x, because DA=CE, then DE? =CD？ +CE？ =CD？ +DA？

=x？ +(8-x)？ =2(x-4)？ +32(0≤x≤8)

It is easy to see that when x=4, the minimum DE is four times the root number 2.

So choose B.