Bioluminescence was shown by the phylum (a) Porifera (b) Ctenophora (c) Coelentrata (d) Mollusca

In this step, we will analyze all the given options to recognize which phylum is known for displaying bioluminescence. (a) Porifera - The phylum Porifera comprises of aquatic, primarily marine, species like sponges. They do not demonstrate bioluminescence and can, therefore, be ruled out. (b) Ctenophora - The phylum Ctenophora, also known as comb jellies, comprises of marine species that are known to exhibit bioluminescence. They have ctenes, comb-like plates of fused cilia, that emit light as they move. This seems like the right answer. (c) Coelenterata - The phylum Coelenterata consists of species like jellyfish, corals, and sea anemones. Some species in this phylum do display bioluminescence, but it is not as prominent or widespread as in Ctenophora. (d) Mollusca - Mollusca is a diverse phylum that includes species like snails, clams, and squid. Some members of this phylum, particularly deep-sea cephalopods, display bioluminescence, but it is not specific to the entire phylum.

Based on the analysis in Step 1, we can conclude that the phylum which prominently shows bioluminescence is Ctenophora. So, the correct answer is (b) Ctenophora.