Observations of Radio Waves from Astronomical Objects Suffer from Poorer

Multiple Choice

Observations of radio waves from astronomical objects suffer from poorer resolution than visible observations with the same size dish (or mirror) because

A) the signals are so weak in the radio region.
B) the wavelength of radio waves is much longer than the wavelengths of visible light.
C) radio telescopes are generally much smaller in diameter than optical telescopes.
D) it is very difficult to detect radio waves.
E) radio telescopes don't use solid mirrors.