Functional systems for specific physiological functions are not seen in
A. Annelids
B. Molluscs
C. Arthropods
D. Coelenterates

Hint: They are diploblastic creatures, in which, the body is comprised of two layers of cells:
Ectoderm – One layer makes up the cells outside the body
Endoderm – different structures the internal coating of the body.
They have depressions in their body.

Complete answer:
Practical frameworks for explicit physiological capacities are not found in coelenterates due to the shortfall of organ framework level of body association. They have a tissue framework association.
The mouth is encased by flimsy and short appendages.
The body is radially even.
The assimilation is both intracellular and extracellular.
The sensory system and the circulatory framework are missing.
They discharge and breathe through basic dispersion. The method of proliferation is biogenetic, which is through maturing. The sexual method of multiplication is seen uniquely in a couple of Coelenterates.

Additional information:
Scyphozoa
They are discovered only in the marine climate.
Medusa is prevailing and umbrella-formed.
Polyps are absent.
Mesogloea is a cell.
Coelenterata is a term incorporating the creature phyla Cnidaria (coral creatures, genuine jams, ocean anemones, ocean pens, and their partners) and Ctenophora (brush jams). They have extremely basic tissue association, with just two layers of cells (outer and inner), and spiral balance. A few models are corals, which are commonly frontier, and hydra, jellyfish and ocean anemones which are single.

So the correct answer is coelenterates.

Note:
Coelenterata come up short on a particular circulatory framework depending rather on dissemination across the tissue layers.
These are generally oceanic or marine environment creatures.
These species show a tissue-level association.