Which sequence of formation is most likely to be correct, oldest ...

[cmoore54]

Which sequence of formation is most likely to be correct, oldest to youngest?
 
  A) globular clusters, open clusters, OB associations
  B) Population I stars, population II stars, population III stars
  C) halo, spiral arms, globular clusters
  D) planetary nebulae, Population I stars, population II stars
  E) emission nebulae, planetary nebulae, dark nebulae

Question 2

Contrast the compositions and heights of the clouds of Earth and Venus.
 
  What will be an ideal response?

[jamesnevil303]

Answer to Question 1

A

Answer to Question 2

Our clouds of water droplets occur in our troposphere, within about 12 km of the surface. On Venus, the much thicker upper-level cloud deck of sulfuric acid droplets lies about 50-70 km above its surface.

[cmoore54]

Thank you!

[jamesnevil303]

Always glad to help...