Many biofilm-specific phenotypes are controlled by ""quorum sensing."" this system allows bacteria to regulate gene expression according to the concentration

Many biofilm-specific phenotypes are controlled by "quorum sensing." This system allows bacteria to regulate gene expression according to the concentration of bacteria.

Explanation:

Quorum sensing is basically a process which depends upon the density dependent communication of bacteria. Higher the number of bacteria, more will be the communication. Example of quorum sensing is biofilms which grow on various surfaces.

Some auto-inducers like peptides and N-acyl homoserine lactone are produced by bacteria during this process which in turn activate some transcription factors to cause gene expression.

In bacteria, it mainly serves the purpose of bioluminescence, sporulation and nitrogen fixation.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.

the answer is b.) hydrogen bonds between bases.