Final answer:
Contrast is the difference in appearance between objects and their background, crucial for microscopy. Techniques like staining and phase-contrast microscopy are used to enhance contrast for better visualization.
Step-by-step explanation:
The correct answer to the question is B) Contrast. Contrast is defined as the difference in intensity between objects and the background on which they are observed. When working with microscopy, many times the samples do not absorb much light which leads to a lack of contrast making it hard to interpret the image. To enhance contrast, various techniques can be used such as staining with dyes or fluorophores for specific applications or employing wave interference techniques. Another method is using phase-contrast microscopy, where light passing through the sample is altered in phase, enhancing contrast due to the interference when light rays superimpose in the image plane, using a device known as a phase plate. Overall, contrast plays a crucial role in the differentiation and visualization of microscopic samples.