Final answer:
Mueller-Hinton agar, with a pH between 7.2 and 7.4, is a standardized, nutrient-rich medium designed for antibiotic susceptibility testing and uniform use across labs.
Step-by-step explanation:
The student has asked which type of agar, with a pH between 7.2 and 7.4, is poured to a depth of 4mm in Petri dishes. The description provided is characteristic of standardized media, specifically designed for uniform use across different laboratories. Mueller-Hinton agar (MHA) is a specialized formulation often used in such applications, particularly for antibiotic susceptibility testing. It is prepared with a lower concentration of agar to ensure that the antibiotics adequately diffuse into the medium. MHA is neither rich nor deficient in nutrients;
it is not designed to be selective or differential in the identification of bacterial species. Considering the standard pH range and the context provided, the correct answer is A) Nutrient-rich agar. This medium facilitates antibiotic diffusion and maintains consistency across various labs, which is crucial for obtaining reliable and comparable analytical results.