Molecular Hydrogen Is Not Very Useful for Mapping Molecular Clouds

Molecular hydrogen is not very useful for mapping molecular clouds because:

A) molecular hydrogen does not occur in most molecular clouds.
B) molecular hydrogen puts out radiation similar to most stars.
C) molecular hydrogen and atomic hydrogen cannot be distinguished in telescopes.
D) radiation from carbon monoxide overwhelms radiation from molecular hydrogen.
E) molecular hydrogen is essentially invisible in the radio portion of the spectrum.