1. Which staining technique would be most appropriate for visualizing the capsule surrounding certain bacteria? A. Negative stain B. Gram stain C. Acid-fast stain D. Simple stain Answer: A. Negative stain Rationale: The negative stain technique uses a dye that stains the background but not the cells, making the capsule, which does not take up the stain, visible against the contrasting background. 2. When preparing a slide for Gram staining, what is the purpose of applying iodine? A. To fix the bacteria to the slide B. To act as a mordant C. To decolorize the cells D. To counterstain the cells Answer: B. To act as a mordant Rationale: Iodine is used as a mordant in Gram staining to enhance the binding of the primary stain (crystal violet) to the cell walls of Grampositive bacteria. 3. In microscopy, what is the function of the oil immersion lens? A. To decrease light refraction B. To increase the resolution C. To magnify the image D. To enhance contrast Answer: B. To increase the resolution Rationale: The oil immersion lens is used with a drop of oil to fill the space between the lens and the slide, reducing light refraction and increasing the resolution of the image. 4. What is the primary reason for heat-fixing a bacterial smear before staining? A. To kill the bacteria B. To adhere the bacteria to the slide C. To enhance the uptake of stain