Final answer:
Bacterial cells can be most effectively visualized with a scanning electron microscope because this type of microscope provides detailed information about the surface characteristics and overall shape of the cells.
Step-by-step explanation:
The scanning electron microscope (SEM) is most effective in visualizing surfaces and the three-dimensional structure of samples. Given the choices provided, bacterial cells would be the most effectively visualized with a scanning electron microscope. The reason for this is that a scanning electron microscope can provide detailed information about the cell's surface characteristics and overall shape, being particularly useful for studying the complex topography of bacterial cells.
When looking at options such as cell organelles, DNA strands, and protein molecules, these can also be visualized by electron microscopy, but they are not as effectively showcased by the SEM as they are with transmission electron microscopy (TEM) for internal structures or atomic force microscopy (AFM) for looking at protein molecules on an atomic level.