a) Transmission electron microscope (TEM ) is able to determine the positions of atoms in the material, which made this type of microscope a significant tool for research and development of nanotechnology. Because of the images with high enough resolution, scientists are using it to examine biological material such as microorganisms and cells.Therefore, to analyze the surface of a cell, this type of microscope is very suitable.
b) In general, the TEM resolution is typically with an order of magnitude higher than that of Scanning Electron Microscopes (SEM), but because the image produced by scanning microscopes, based more on surface processes rather than transmission,SEM is able to view the larger samples, and has a much greater penetration depth, producing images that are a good three-dimensional representation of the sample. That's why, SEM is considered more suitable to analyze a section of brain tissue.
c) For analyzing a small insect abouy 1mm long, a stereo microscope (dissecting microscope ) could be a suitable choice, because with this one there could be captured three-dimensional images of the specimen. Of course, also SEM could be a great choice.