Which of the following gases, which we might be able to detect in infrared spectra, would be a strong indicator of life on another planet?
A) carbon dioxide
B) ozone
C) methane
D) water vapor
E) sulfuric acid
Question 2
Which sequence of formation by age is correct, oldest to youngest?
A) Dark nebulae, planetary nebulae, emission nebulae
B) Spiral arms, bulge, halo
C) Halo, spiral arms, globular clusters
D) Globular clusters, emission nebulae, open clusters