Why Will Proposed Future Experiments to Search for Earthlike Planets

Multiple Choice

Why will proposed future experiments to search for Earthlike planets use the infrared portion of the spectrum?

A) Earth's atmosphere is more transparent over this wavelength range than at any other wavelength.
B) Only at these wavelengths will spectra show spectral signatures that are identifiable as originating on Earthlike planets.
C) The ratio of IR to visible radiation from planets is much higher than for their parent stars.
D) It is the easiest spectral range to study from ground-based telescopes.