Radio waves are diffracted by large objects such as buildings, whereas light is not noticeably diffracted by large objects such as buildings. Why is this?

Choose one answer.
a. Radio waves are unpolarized, whereas light is plane polarized.
b. The wavelength of light is much smaller than the wavelength of radio waves.
c. Light is coherent and radio waves are usually not coherent.
d. Radio waves are coherent and light is usually not coherent.