Phylum Level of organization Digestive system Respiratory system Aschelminthes A Complete Absent Echinodermata Organ system B Present Platyhelminthes Organ Incomplete C Annelida Organ system Incomplete D Select the option with correct identification of A, B, C, and D.

Step-by-step solution

I. Levels of the organization - It is of various types A. Cellular level - Division of labour is there between the cells but are not tissues. These are in the form of loose cell aggregates. Example: Sponges (Porifers) B. Tissue level - Cells that are organized to perform the same function act as tissues. Examples: Coelenterates. C. Organ level - Tissues grouped together to form organs. Examples: Platyhelminthes. D. Organ system level - Organs associated to form functional systems. Examples: Annelids, arthropods, mo