Final answer:
The group of Echinoderms that contains both sessile and motile species is Crinoidea.
Step-by-step explanation:
The group or lineage of Echinoderms that contains both sessile species and motile species is Crinoidea. Crinoidea, also known as sea lilies or feather stars, are immobile echinoderms that attach themselves to a substrate using a stalk or stem. They have feathery arms that allow them to filter feed while being anchored to the substrate. Therefore, the correct answer is Crinoidea (b).