Given the Presence of Dust Throughout the Disk of the Milky

Given the presence of dust throughout the disk of the Milky Way Galaxy, what is the best technique for learning about more distant regions of our galaxy's disk.

A) look for blue radiation from stars and nebulae, since the light is reddened
B) look for red light from stars and nebulae
C) look for radiation at long wavelengths, for example in the infrared region of the spectrum
D) look for HII regions, whose high-energy radiation penetrates dust
E) send a spacecraft to Pluto, from where we can see above the Galaxy's disk