The 21-Cm Line Is One of the Most Important Wavelengths

The 21-cm line is one of the most important wavelengths in radio astronomy. The fact that it is a relatively long wavelength is important because long wavelengths

A) are more likely to interact with clouds of gas and dust.
B) are more likely to pass through clouds of gas and dust.
C) carry more energy than short wavelengths of the same energy.
D) can be detected with greater resolution than can short wavelengths.