What type of sample preparation is most commonly used when observing living cells under a compound light microscope?

When observing living cells under a compound light microscope, the most suitable sample preparation method is a wet mount. A wet mount involves placing a drop of liquid, typically water or a suitable buffer, on a microscope slide, followed by gently placing a coverslip over the sample. This method allows the cells to remain hydrated and alive, making it possible to observe their natural behavior and processes in real-time, such as movement, division, or interaction with their environment.

Wet mounts are essential for studying living specimens because they preserve the natural state of the cells and provide the necessary environment for them to function as they would in their native conditions. This technique is particularly useful for observing microorganisms, such as bacteria and protozoa, as well as animal and plant cells.

Other methods, such as fixation and staining, typically involve killing the cells or altering their natural state, which makes them unsuitable for studying living specimens. Fixation preserves the structure of cells but usually involves chemical agents that can destroy cellular viability. Smearing is a technique often used to prepare samples for microscopy, but it is more applicable to fixed specimens rather than living ones. Staining enhances the contrast of biological structures but often requires cells to be dead for the stain to adhere properly. Therefore, using a wet