The Size of the Smallest Things That Can Be Seen

Multiple Choice

The size of the smallest things that can be seen with an optical microscope is limited by diffraction.Which of the following could help a microscopist see smaller things?

A) A more powerful microscope could be used.
B) The microscope could have a lens with a shorter focal length.
C) The microscope could have a lens with a longer focal length.
D) The diameter of the lens could be smaller.
E) Light with a shorter wavelength could be used.