( a ) bilaterally symmetrical, triploblastic and coelomate animals with organ level of body organisation
( b ) bilaterally symmetrical, triploblastic, metamerically segmented and coelomate animals with organ-system level of body organisation
( c ) bilaterally symmetrical, diploblastic and acoelomate animals with organ-system level of body organisation
( d ) bilaterally symmetrical, triploblastic and pseudocoelomate animals with organ-system level of body organisation
