The light microscope employs visible light to detect small things. But it produces lower-resolution images than an electron microscope (this image is probably from an electron microscope). So, as the images are in a lower resolution, C is wrong, because a lower resolution would not show more detail of the cells' structure.
The light microscope allows us to see the image that is focused by light, but the light can only illuminate the outer layer of the object. That's way the object must be really thin, to allow the light to transpass it. But even if the object is extra thin, the light microscope still can show only a two dimensional image. Therefore, A is incorrect.
There is no equipment capable of show the atoms, as the atoms are the smallest unit that creates all things. Therefore, D is also incorrect.
As it was said before, the lght microscope shows the images in a lower resolution. Therefore, it shows less details of the cells' strucutre. This means that the correct answer is B.The light microscope would show less detail of the cells' structure.