When would you use a dry mount to view a specimen under a microscope?:
A dry mount is exactly as it sounds: the thing you plan to observe is placed on the slide with a cover slip over it. No water is needed. This kind of mount is usually used for inanimate objects or things that do not need water to live.
When would you use a wet mount?:
In a wet mount, the specimen is placed in a drop of water or other liquid held between the slide and the cover slip by surface tension. This method is commonly used, for example, to view microscopic organisms that grow in pond water or other liquid media, especially when studying their movement and behavior.