Porifera have been long debated to be in the Kingdom Protista, not the Kingdom Animalia. Why might this argument hold ground?

A) Porifera are triploblastic and have no distinct tissues.
B) Porifera are acoelomates and are atriploblastic.
C) Porifera have no distinct tissues and are sessile.
D) Porifera have no distinct tissues and no cavity between layers.
E) Porifera are sessile and are pseudocoelomatic.