Final answer:
Phenylethyl alcohol agar (PEA) is a type of selective media that allows the growth of gram-positive bacteria while inhibiting gram-negative bacteria. So option (B) is correct.
Step-by-step explanation:
Phenylethyl alcohol agar (PEA) falls into the category of selective media. Selective media are designed to support the growth of certain microorganisms while inhibiting the growth of others. PEA is particularly known for inhibiting the growth of gram-negative bacteria while allowing gram-positive bacteria to grow, therefore facilitating the isolation of the latter. By including agents such as phenylethyl alcohol, PEA media restrict the growth of unwanted microorganisms and provide an environment conducive to the growth of desired organisms. These properties make PEA a valuable tool in the identification of gram-positive bacteria in clinical specimens.
Selective media like PEA agar are particularly useful in clinical microbiology laboratories for the isolation of specific groups of bacteria. For example, PEA agar can be employed to isolate staphylococci from mixed cultures, as staphylococci are generally gram-positive bacteria.