Final answer:
Selective media would be useful for isolating bacteria that are in small numbers in a mixed culture. Option e.
Step-by-step explanation:
To isolate bacteria that are in small numbers in a mixed culture, selective media would be useful. Selective media contain substances that inhibit the growth of unwanted microorganisms while supporting the growth of the desired bacteria. This helps to reduce competition and isolate the bacteria of interest.
Examples of selective media include MacConkey agar, which contains bile salts and crystal violet that favor the growth of gram-negative bacteria, and inhibit the growth of gram-positive bacteria.
In contrast, differential media allow us to distinguish between different bacterial types based on differences in growth patterns. It is not specifically designed for isolating bacteria in small numbers.
Option e.