What is the primary use of a microscope slide in a lab setting?

The primary use of a microscope slide in a lab setting is to support and hold specimens for observation. When preparing a sample for microscopic examination, the slide provides a flat, stable surface on which the specimen can be placed. This allows for clear visualization of the biological material or other samples under the microscope. Properly prepared slides enable scientists to observe cellular structures, tissues, or microorganisms with enhanced focus and clarity.

In contrast, the other choices mention functions that are not related to microscope slides. Conducting chemical reactions typically requires beakers or test tubes. Measuring liquid substances is done with graduated cylinders or pipettes. Analyzing gas samples involves different equipment, like gas syringes or gas chromatographs. Therefore, the slide's designated purpose is clearly focused on the support and observation of specimens.