Why is it that with a standard transmission electron microscope, resolution is actually about two orders of magnitude less than its theoretical limit?

A)The lenses of an electron microscope exhibit serious spherical aberration problems, which can be avoided by using a very small N. A.
B)The lenses of an electron microscope exhibit serious spherical aberration problems, which can be avoided by using a very large N. A.
C)If electron wavelength is too high, spherical aberration distorts the image.
D)If electron wavelength is too low, spherical aberration distorts the image.