Regarding to building perfect phylogeny, which alternative is correct:

a) - Is not possible to build a perfect phylogeny without a root
b) - If the characteristics in a character state matrix are not binary, build a perfect phylogeny is trivial
c) - In a perfect phylogeny, a event to a characteristics cannot appear twice in the tree 
d) - Character state matrices are always square matrices 
e) - none of the above

Original idea by: Guilherme de Mello Barsoti