A:why
B:whe
C:how
D:where
No one knows for sure why adolescence is unique ____ humans.
三角形的三边都为整数,其中两边长为3和7,最长边第三边的取值有( )
集合P=P=n|n=lnk,k∈N*,若a,b∈P,则a⊕b∈P,那么运算⊕可能是( )