Final answer:
Xylose lysine deoxycholate (XLD) agar is a selective, differential, and complex medium used in microbiology to grow and differentiate certain types of bacteria, such as pathogens from the Enterobacteriaceae family.
Step-by-step explanation:
Xylose lysine deoxycholate (XLD) agar is a type of medium used in microbiology. This medium serves multiple purposes and is characterized as a selective medium, a differential medium, and a complex medium. As a selective medium, XLD agar is designed to encourage the growth of certain microorganisms, such as Salmonella and Shigella, while inhibiting others, particularly non-pathogenic bacteria from the gut.
It also functions as a differential medium because it contains indicators like lysine and xylose, allowing for the distinction between organisms that can ferment xylose and those that cannot. This differentiation is evident through the color change of the colonies or the medium itself. Lastly, XLD is a complex medium because it includes components like yeast extract and sodium deoxycholate, the exact chemical amounts of which are not precisely known, unlike in chemically defined media.
Therefore, the correct answer to the question about the characterization of XLD agar would be selection D, a selective medium, a differential medium, and a complex medium.