You would use the 21-cm radio emission line to map out ____________.
A)the interstellar medium
B)molecular clouds
C)atomic hydrogen clouds
D)All of the other choices are correct.

Question

Quizplus · Accepted Answer

The 21-cm radio emission line is associated with the spin-flip transition of atomic hydrogen. Therefore, it is primarily used to map the distribution of atomic hydrogen clouds in our galaxy and other galaxies.

You Would Use the 21-Cm Radio Emission Line to Map