Final answer:
Phase-contrast microscopy is the type of microscopy most similar to negative staining for producing images of unstained cells, as it increases contrast without the need for stains, making it ideal for viewing live specimens.
Step-by-step explanation:
The type of microscopy that produces an image of unstained cells most similar to the one achieved by negative staining is phase-contrast microscopy. This technique enhances contrast between various parts of a specimen, such as cells or organelles with different refractive indices, without the need for staining. In contrast to bright-field microscopy, phase-contrast microscopy allows for the observation of live, unstained cells by creating an inherent contrast that makes internal cellular structures much more visible. This is particularly useful for live specimens, where staining methods are not desirable or feasible.
Darkfield microscopy, which is not listed as an option here, is another useful technique that allows for the visualization of specimens that are invisible under standard bright-field conditions without staining, but given the options provided, phase-contrast microscopy is the most similar to negative staining in terms of the visual results it provides. Both techniques are valuable for enhancing the visibility of unstained cells, with phase-contrast microscopy being more cost-effective and commonly used for observing live specimens.