When you look at an image of a galaxy, you can see many dark features. What are they?
A. These dark features are interstellar gas and dust that do not have any atomic level transitions and hence generate no light of its own.
B. These dark features are presence of dark matter that has a huge gravitational pull, but are not visible.
C. These dark features are interstellar gas and dust that are blocking the light from stars that are behind them.
D. These dark features are generated by presence of Black Holes that keep absorbing all light.