Final answer:
The staining procedure that employs both a primary dye and a counterstain is c) Differential stain. This technique, such as Gram staining, differentiates organisms based on their interactions with multiple stains, unlike the capsule stain which typically uses a negative staining technique.
Step-by-step explanation:
Differential Staining Techniques
In microbiology, differential stains are critical for examining cellular structures and for distinguishing between different types of bacteria. A notable characteristic of differential staining is the use of a primary stain and a counterstain in the procedure. One of the most recognized differential staining techniques is Gram staining, which employs crystal violet as the primary stain and a secondary counterstain to differentiate between gram-positive and gram-negative bacteria. Another example is the endospore stain, which reveals whether bacteria are capable of forming protective endospores. Despite being listed as an option, the capsule stain is typically performed using a negative staining technique, meaning it does not follow the pattern of using a primary dye followed by a counterstain since it aims to stain the background but not the capsule itself.
Based on the definitions and examples provided, the answer to the student's question is c) Differential stain since this is the staining procedure that utilizes both a primary dye and a counterstain to distinguish between different cell types or cell structures. The choice such as simple stain, capsule stain, or the invented 'μltiple choice stain' do not employ both types of stains in the manner described.