Diversity in Living Organisms

The ctenophores are diploblastic with a biradial symmetry or modified radial  (with an underlying bilateral symmetry), which is a bit different than the radial symmetry typical of cnidarian.

Sea Walnut (Pleurobrachia) belongs to the phylum Ctenophora. These organisms are radially symmetrical, diploblastic, marine, and exhibit bioluminescence.

Boroe is a type of comb jelly and has a body structure that is transparent and sac like with a mouth at one end. The gastrovascular channels are beneath the cilia and the animal lacks any tentacles otherwise. So, the correct answer is 'Boroe.

Comb jellies are oval-shaped animals with eight rows of tiny comb-like plates that they beat to move through the water.  They are gelatinous animals belonging to the phylum of animals that live in marine waters worldwide, ctenophora.
Thus, the correct answer is option D.

Some animals are three layered with ectoderm, endoderm and mesoderm called triploblastic.  Ctenophores have two main layers of cells that sandwich a middle layer of jelly-like material, which is called the mesoglea. So, even though the layers of tisse are diploblastic the presence of the third jelly-like layer gives them an intermediate stage.

Comb plates are the characteristic feature of phylum Ctenophora. Pleurobrachia is a well-known example of a ctenophore.

Biradial symmetry is a combination of radial and bilateral symmetry, as in the ctenophores. Here, the body components are arranged with similar parts on either side of a central axis, and each of the four sides of the body is identical to the opposite side but different from the adjacent side. Also, Cnidblasts being exclusive Cnidarian character does not exist in Ctenophora.

In Ctenophores, the digestion is predominantly completed in the stomadaeum(extracellular). The undigested food passes out either throught the mouth or the anal pores. 

Statocysts are a balance organ present in ctenophores. This provides equilibriuim for the organism while swimming. These statocysts are situated away from the oral or mouth region also called the aboral region. 

Boroe is a transparent comb jelly with sac-like body with a mouth on one side and gonads internally present. However, it lacks any tentacles. So, the correct answer is 'Tentacles'.

The tentacles of Ctenophores have meridonial bands with transversely arranged combs like structures. Comb-like eight ciliary plates on the body serve the purpose of locomotion. 

Ctenophores use their tentacles to capture their prey and these tentacles are made of specialized cells called colloblast. These colloblast are made of axial filaments and a granular sticky dome.

While Beroe have a sac like transparent body, Hormiphora have a pear shaped body. Ctenoplana has a circular and flattened body. So, the correct answer is 'Flat bilobed body'.